diff --git a/platform/core/src/redux/reducers/viewports.js b/platform/core/src/redux/reducers/viewports.js
index 2a6d66ee0..e96444f09 100644
--- a/platform/core/src/redux/reducers/viewports.js
+++ b/platform/core/src/redux/reducers/viewports.js
@@ -11,20 +11,63 @@ import {
   SET_VIEWPORT_LAYOUT_AND_DATA,
 } from './../constants/ActionTypes.js';
 
-const DEFAULT_STATE = {
+export const DEFAULT_STATE = {
   numRows: 1,
   numColumns: 1,
   activeViewportIndex: 0,
   layout: {
-    viewports: [
-      {
-        // plugin: 'cornerstone',
-      },
-    ],
+    viewports: [{}],
   },
   viewportSpecificData: {},
 };
 
+/**
+ *  Take the new number of rows and columns, delete all not used viewport data and also set
+ *  active viewport as default in case current one is not available anymore.
+ *
+ * @param {Number} numRows
+ * @param {Number} numColumns
+ * @param {Object} currentViewportSpecificData
+ * @returns
+ */
+const findActiveViewportSpecificData = (
+  numRows,
+  numColumns,
+  currentViewportSpecificData = {}
+) => {
+  const numberOfViewports = numRows * numColumns;
+  const viewportSpecificData = cloneDeep(currentViewportSpecificData);
+
+  if (numberOfViewports < Object.keys(viewportSpecificData).length) {
+    Object.keys(viewportSpecificData).forEach(key => {
+      if (key > numberOfViewports - 1) {
+        delete viewportSpecificData[key];
+      }
+    });
+  }
+
+  return viewportSpecificData;
+};
+/**
+ *  Take new number of rows and columns and make sure the current active viewport index is still available, if not, return the default
+ *
+ * @param {Number} numRows
+ * @param {Number} numColumns
+ * @param {Number} currentActiveViewportIndex
+ * @returns
+ */
+const getActiveViewportIndex = (
+  numRows,
+  numColumns,
+  currentActiveViewportIndex
+) => {
+  const numberOfViewports = numRows * numColumns;
+
+  return currentActiveViewportIndex > numberOfViewports - 1
+    ? DEFAULT_STATE.activeViewportIndex
+    : currentActiveViewportIndex;
+};
+
 /**
  * The definition of a viewport action.
  *
@@ -50,7 +93,12 @@ const viewports = (state = DEFAULT_STATE, action) => {
      * @return {Object} New state.
      */
     case SET_VIEWPORT_ACTIVE: {
-      return { ...state, activeViewportIndex: action.viewportIndex };
+      const activeViewportIndex = getActiveViewportIndex(
+        state.numRows,
+        state.numColumns,
+        action.viewportIndex
+      );
+      return { ...state, activeViewportIndex };
     }
 
     /**
@@ -59,11 +107,25 @@ const viewports = (state = DEFAULT_STATE, action) => {
      * @return {Object} New state.
      */
     case SET_VIEWPORT_LAYOUT: {
+      const { numRows, numColumns } = action;
+      const viewportSpecificData = findActiveViewportSpecificData(
+        numRows,
+        numColumns,
+        state.viewportSpecificData
+      );
+      const activeViewportIndex = getActiveViewportIndex(
+        numRows,
+        numColumns,
+        state.activeViewportIndex
+      );
+
       return {
         ...state,
         numRows: action.numRows,
         numColumns: action.numColumns,
         layout: { viewports: [...action.viewports] },
+        viewportSpecificData,
+        activeViewportIndex,
       };
     }
 
@@ -73,12 +135,25 @@ const viewports = (state = DEFAULT_STATE, action) => {
      * @return {Object} New state.
      */
     case SET_VIEWPORT_LAYOUT_AND_DATA: {
+      const { numRows, numColumns } = action;
+      const viewportSpecificData = findActiveViewportSpecificData(
+        numRows,
+        numColumns,
+        action.viewportSpecificData
+      );
+      const activeViewportIndex = getActiveViewportIndex(
+        numRows,
+        numColumns,
+        state.activeViewportIndex
+      );
+
       return {
         ...state,
         numRows: action.numRows,
         numColumns: action.numColumns,
         layout: { viewports: [...action.viewports] },
-        viewportSpecificData: cloneDeep(action.viewportSpecificData),
+        viewportSpecificData,
+        activeViewportIndex,
       };
     }
 
diff --git a/platform/core/src/redux/reducers/viewports.test.js b/platform/core/src/redux/reducers/viewports.test.js
index 879fabc23..c7d3fe5a2 100644
--- a/platform/core/src/redux/reducers/viewports.test.js
+++ b/platform/core/src/redux/reducers/viewports.test.js
@@ -1,35 +1,61 @@
-// https://medium.com/@netxm/testing-redux-reducers-with-jest-6653abbfe3e1
-import reducer from './viewports.js';
+import { Reducer } from 'redux-testkit';
+
+import reducer, { DEFAULT_STATE } from './viewports.js';
 import * as types from './../constants/ActionTypes.js';
 
 describe('viewports reducer', () => {
   it('should return the initial state', () => {
-    expect(reducer(undefined, {})).toEqual({
-      activeViewportIndex: 0,
-      numRows: 1,
-      numColumns: 1,
-      layout: {
-        viewports: [{}],
-      },
-      viewportSpecificData: {},
-    });
+    expect(reducer(undefined, {})).toEqual(DEFAULT_STATE);
   });
 
-  it('should handle SET_VIEWPORT_ACTIVE', () => {
-    const setViewportActiveAction = {
+  it('should handle SET_VIEWPORT_ACTIVE with inexistent viewport index', () => {
+    const initialState = {
+      numRows: 4,
+      numColumns: 4,
+      activeViewportIndex: 0,
+    };
+
+    const action = {
       type: types.SET_VIEWPORT_ACTIVE,
       viewportIndex: 100,
     };
 
-    const updatedState = reducer({}, setViewportActiveAction);
+    const expectedToChangeInState = {
+      activeViewportIndex: 0,
+    };
 
-    expect(updatedState.activeViewportIndex).toEqual(
-      setViewportActiveAction.viewportIndex
-    );
+    Reducer(reducer)
+      .withState(initialState)
+      .expect(action)
+      .toChangeInState(expectedToChangeInState);
+  });
+
+  it('should handle SET_VIEWPORT_ACTIVE with existent viewport index', () => {
+    const initialState = {
+      numRows: 4,
+      numColumns: 4,
+      activeViewportIndex: 0,
+    };
+
+    const action = {
+      type: types.SET_VIEWPORT_ACTIVE,
+      viewportIndex: 5,
+    };
+
+    const expectedToChangeInState = {
+      activeViewportIndex: 5,
+    };
+
+    Reducer(reducer)
+      .withState(initialState)
+      .expect(action)
+      .toChangeInState(expectedToChangeInState);
   });
 
   it('should handle SET_VIEWPORT_LAYOUT', () => {
-    const setViewportLayoutAction = {
+    const initialState = DEFAULT_STATE;
+
+    const action = {
       type: types.SET_VIEWPORT_LAYOUT,
       numRows: 1,
       numColumns: 2,
@@ -43,18 +69,193 @@ describe('viewports reducer', () => {
       ],
     };
 
-    const updatedState = reducer({}, setViewportLayoutAction);
+    const expectedToChangeInState = {
+      numRows: 1,
+      numColumns: 2,
+      layout: {
+        viewports: [
+          {
+            plugin: 'cornerstone',
+          },
+          {
+            plugin: 'vtk',
+          },
+        ],
+      },
+    };
 
-    expect(updatedState.numRows).toEqual(setViewportLayoutAction.numRows);
-    expect(updatedState.numColumns).toEqual(setViewportLayoutAction.numColumns);
-    expect(updatedState.layout.viewports).toEqual(
-      setViewportLayoutAction.viewports
-    );
+    Reducer(reducer)
+      .withState(initialState)
+      .expect(action)
+      .toChangeInState(expectedToChangeInState);
+  });
+
+  it('should handle SET_VIEWPORT_LAYOUT when we reduce the number of viewports', () => {
+    const initialState = {
+      numRows: 1,
+      numColumns: 2,
+      viewportSpecificData: {
+        0: { viewportData0: 'viewportData0' },
+        1: { viewportData1: 'viewportData1' },
+      },
+      layout: {
+        viewports: [],
+      },
+      activeViewportIndex: 0,
+    };
+
+    const action = {
+      type: types.SET_VIEWPORT_LAYOUT,
+      numRows: 1,
+      numColumns: 1,
+      viewports: [],
+    };
+
+    const expectedState = {
+      numRows: 1,
+      numColumns: 1,
+      viewportSpecificData: {
+        0: { viewportData0: 'viewportData0' },
+      },
+      layout: {
+        viewports: [],
+      },
+      activeViewportIndex: 0,
+    };
+
+    Reducer(reducer)
+      .withState(initialState)
+      .expect(action)
+      .toReturnState(expectedState);
+  });
+
+  it('should handle SET_VIEWPORT_LAYOUT_AND_DATA', () => {
+    const initialState = {
+      numRows: 1,
+      numColumns: 1,
+      viewportSpecificData: {
+        0: { viewportData0: 'data0' },
+      },
+      layout: {
+        viewports: [{ plugin: 'cornerstone' }],
+      },
+      activeViewportIndex: 0,
+    };
+
+    const action = {
+      type: types.SET_VIEWPORT_LAYOUT_AND_DATA,
+      numRows: 1,
+      numColumns: 2,
+      viewports: [{ plugin: 'cornerstone' }, { plugin: 'cornerstone' }],
+      viewportSpecificData: {
+        0: { viewportData0: 'NEWdata0' },
+        1: { viewportData1: 'NEWdata1' },
+      },
+    };
+
+    const expectedState = {
+      numRows: 1,
+      numColumns: 2,
+      viewportSpecificData: {
+        0: { viewportData0: 'NEWdata0' },
+        1: { viewportData1: 'NEWdata1' },
+      },
+      layout: {
+        viewports: [{ plugin: 'cornerstone' }, { plugin: 'cornerstone' }],
+      },
+      activeViewportIndex: 0,
+    };
+
+    Reducer(reducer)
+      .withState(initialState)
+      .expect(action)
+      .toReturnState(expectedState);
+  });
+
+  it('should handle SET_VIEWPORT_LAYOUT_AND_DATA when we reduce the number of viewports', () => {
+    const initialState = {
+      numRows: 1,
+      numColumns: 3,
+      viewportSpecificData: {
+        0: { viewportData0: 'vtkData0' },
+        1: { viewportData1: 'vtkData1' },
+        2: { viewportData2: 'vtkData2' },
+      },
+      layout: {
+        viewports: [{ plugin: 'vtk' }, { plugin: 'vtk' }, { plugin: 'vtk' }],
+      },
+      activeViewportIndex: 0,
+    };
+
+    const action = {
+      type: types.SET_VIEWPORT_LAYOUT_AND_DATA,
+      numRows: 1,
+      numColumns: 1,
+      viewports: [{ plugin: 'cornerstone' }],
+      viewportSpecificData: {
+        0: { viewportData0: 'cornerstoneData0' },
+      },
+    };
+
+    const expectedState = {
+      numRows: 1,
+      numColumns: 1,
+      viewportSpecificData: {
+        0: { viewportData0: 'cornerstoneData0' },
+      },
+      layout: {
+        viewports: [{ plugin: 'cornerstone' }],
+      },
+      activeViewportIndex: 0,
+    };
+
+    Reducer(reducer)
+      .withState(initialState)
+      .expect(action)
+      .toReturnState(expectedState);
+  });
+
+  it('should handle SET_VIEWPORT when we only set one viewport specific data', () => {
+    const initialState = {
+      numRows: 1,
+      numColumns: 2,
+      viewportSpecificData: {
+        0: { viewportData0: 'data0' },
+        1: { viewportData1: 'data1' },
+      },
+      layout: {
+        viewports: [{ plugin: 'cornerstone' }, { plugin: 'cornerstone' }],
+      },
+      activeViewportIndex: 0,
+    };
+
+    const action = {
+      type: types.SET_VIEWPORT,
+      viewportIndex: 1,
+      viewportSpecificData: {
+        viewportData1: 'NEWdata1',
+      },
+    };
+
+    const expectedState = {
+      numRows: 1,
+      numColumns: 2,
+      viewportSpecificData: {
+        0: { viewportData0: 'data0' },
+        1: { viewportData1: 'NEWdata1' },
+      },
+      layout: {
+        viewports: [{ plugin: 'cornerstone' }, { plugin: 'cornerstone' }],
+      },
+      activeViewportIndex: 0,
+    };
+
+    Reducer(reducer)
+      .withState(initialState)
+      .expect(action)
+      .toReturnState(expectedState);
   });
 
-  // If there were previous keys, this would have
-  // "merge" behavior, not a clear & set
-  // May be worth another test?
   it('should handle SET_VIEWPORT', () => {
     const viewportToSet = 0;
     const setViewportAction = {