diff --git a/invesalius/constants.py b/invesalius/constants.py
index 6fcdc48..924db39 100644
--- a/invesalius/constants.py
+++ b/invesalius/constants.py
@@ -475,6 +475,8 @@ ID_SWAP_XY = wx.NewId()
 ID_SWAP_XZ = wx.NewId()
 ID_SWAP_YZ = wx.NewId()
 
+ID_BOOLEAN_MASK = wx.NewId()
+
 #---------------------------------------------------------
 STATE_DEFAULT = 1000
 STATE_WL = 1001
@@ -565,3 +567,7 @@ PROJECTION_CONTOUR_MIDA=8
 #------------ Projections defaults ------------------
 PROJECTION_BORDER_SIZE=1.0
 PROJECTION_MIP_SIZE=2
+
+# ------------- Boolean operations ------------------
+BOOLEAN_UNION = 1
+BOOLEAN_DIFF = 2
diff --git a/invesalius/control.py b/invesalius/control.py
index d27e7d1..c9c62a1 100644
--- a/invesalius/control.py
+++ b/invesalius/control.py
@@ -82,6 +82,8 @@ class Controller():
         Publisher.subscribe(self.OnOpenRecentProject, 'Open recent project')
         Publisher.subscribe(self.OnShowAnalyzeFile, 'Show analyze dialog')
 
+        Publisher.subscribe(self.ShowBooleanOpDialog, 'Show boolean dialog')
+
 
     def OnCancelImport(self, pubsub_evt):
         #self.cancel_import = True
@@ -628,6 +630,6 @@ class Controller():
                                   preset_name + '.plist')
         plistlib.writePlist(preset, preset_dir)
 
-
-
-
+    def ShowBooleanOpDialog(self, pubsub_evt):
+        dlg = dialogs.MaskBooleanDialog(prj.Project().mask_dict)
+        dlg.ShowModal()
diff --git a/invesalius/data/slice_.py b/invesalius/data/slice_.py
index 106fb10..575cb8e 100644
--- a/invesalius/data/slice_.py
+++ b/invesalius/data/slice_.py
@@ -160,6 +160,8 @@ class Slice(object):
 
         Publisher.subscribe(self._set_projection_type, 'Set projection type')
 
+        Publisher.subscribe(self._do_boolean_op, 'Do boolean operation')
+
         Publisher.subscribe(self.OnExportMask,'Export mask to file')
 
         Publisher.subscribe(self.OnCloseProject, 'Close project data')
@@ -1080,12 +1082,17 @@ class Slice(object):
                 else:
                     node.value += shiftWW * factor
 
-    def do_threshold_to_a_slice(self, slice_matrix, mask):
+    def do_threshold_to_a_slice(self, slice_matrix, mask, threshold=None):
         """ 
         Based on the current threshold bounds generates a threshold mask to
         given slice_matrix.
         """
-        thresh_min, thresh_max = self.current_mask.threshold_range
+        if threshold:
+            thresh_min, thresh_max = threshold
+        else:
+            thresh_min, thresh_max = self.current_mask.threshold_range
+
+        print ">>>> THreshold", thresh_min, thresh_max
         m = (((slice_matrix >= thresh_min) & (slice_matrix <= thresh_max)) * 255)
         m[mask == 1] = 1
         m[mask == 2] = 2
@@ -1106,7 +1113,7 @@ class Slice(object):
         for n in xrange(1, mask.matrix.shape[0]):
             if mask.matrix[n, 0, 0] == 0:
                 m = mask.matrix[n, 1:, 1:]
-                mask.matrix[n, 1:, 1:] = self.do_threshold_to_a_slice(self.matrix[n-1], m)
+                mask.matrix[n, 1:, 1:] = self.do_threshold_to_a_slice(self.matrix[n-1], m, mask.threshold_range)
 
         mask.matrix.flush()
 
@@ -1209,6 +1216,43 @@ class Slice(object):
 
         return blend_imagedata.GetOutput()
 
+    def _do_boolean_op(self, pubsub_evt):
+        op, m1, m2 = pubsub_evt.data
+        self.do_boolean_op(op, m1, m2)
+
+    def do_boolean_op(self, op, m1, m2):
+        name_ops = {const.BOOLEAN_UNION: _(u"Union"), 
+                    const.BOOLEAN_DIFF: _(u"Diff")}
+
+
+        name = u"%s_%s_%s" % (name_ops[op], m1.name, m2.name)
+        proj = Project()
+        mask_dict = proj.mask_dict
+        names_list = [mask_dict[i].name for i in mask_dict.keys()]
+        new_name = utils.next_copy_name(name, names_list)
+
+        future_mask = Mask()
+        future_mask.create_mask(self.matrix.shape)
+        future_mask.name = new_name
+
+        future_mask.matrix[:] = 1
+        m = future_mask.matrix[1:, 1:, 1:]
+
+        self.do_threshold_to_all_slices(m1)
+        m1 = m1.matrix[1:, 1:, 1:]
+
+        self.do_threshold_to_all_slices(m2)
+        m2 = m2.matrix[1:, 1:, 1:]
+
+        if op == const.BOOLEAN_UNION:
+            m[:] = ((m1 > 2) + (m2 > 2)) * 255
+
+        elif op == const.BOOLEAN_DIFF:
+            m[:] = ((m1 > 2) - (m2 > 2)) * 255
+
+        future_mask.was_edited = True
+        self._add_mask_into_proj(future_mask)
+
     def apply_slice_buffer_to_mask(self, orientation):
         """
         Apply the modifications (edition) in mask buffer to mask.
diff --git a/invesalius/gui/dialogs.py b/invesalius/gui/dialogs.py
index c6d7271..577924c 100644
--- a/invesalius/gui/dialogs.py
+++ b/invesalius/gui/dialogs.py
@@ -1384,3 +1384,65 @@ class ClutImagedataDialog(wx.Dialog):
         super(wx.Dialog, self).Show(show)
         if gen_evt:
             self.clut_widget._generate_event()
+
+
+class MaskBooleanDialog(wx.Dialog):
+    def __init__(self, masks):
+        pre = wx.PreDialog()
+        pre.Create(wx.GetApp().GetTopWindow(), -1, style=wx.DEFAULT_DIALOG_STYLE|wx.FRAME_FLOAT_ON_PARENT)
+        self.PostCreate(pre)
+
+        self._init_gui(masks)
+
+    def _init_gui(self, masks):
+        mask_choices = [(masks[i].name, masks[i]) for i in sorted(masks)]
+        self.mask1 = wx.ComboBox(self, -1, mask_choices[0][0], choices=[])
+        self.mask2 = wx.ComboBox(self, -1, mask_choices[0][0], choices=[])
+
+        for n, m in mask_choices:
+            self.mask1.Append(n, m)
+            self.mask2.Append(n, m)
+
+        self.mask1.SetSelection(0)
+        self.mask2.SetSelection(0)
+
+        op_choices = ((u"Union", const.BOOLEAN_UNION),
+                      (u"Difference", const.BOOLEAN_DIFF))
+        self.op_boolean = wx.ComboBox(self, -1, op_choices[0][0], choices=[])
+
+        for n, i in op_choices:
+            self.op_boolean.Append(n, i)
+
+        self.op_boolean.SetSelection(0)
+
+        btn_ok = wx.Button(self, wx.ID_OK)
+        btn_ok.SetDefault()
+
+        btn_cancel = wx.Button(self, wx.ID_CANCEL)
+
+        btnsizer = wx.StdDialogButtonSizer()
+        btnsizer.AddButton(btn_ok)
+        btnsizer.AddButton(btn_cancel)
+        btnsizer.Realize()
+
+        sizer = wx.BoxSizer(wx.VERTICAL)
+        sizer.Add(self.mask1, 1, wx.EXPAND)
+        sizer.Add(self.op_boolean, 1, wx.EXPAND)
+        sizer.Add(self.mask2, 1, wx.EXPAND)
+        sizer.Add(btnsizer, 1, wx.EXPAND)
+
+        self.SetSizer(sizer)
+        sizer.Fit(self)
+
+        self.Centre()
+
+        btn_ok.Bind(wx.EVT_BUTTON, self.OnOk)
+
+    def OnOk(self, evt):
+        op = self.op_boolean.GetClientData(self.op_boolean.GetSelection())
+        m1 = self.mask1.GetClientData(self.mask1.GetSelection())
+        m2 = self.mask2.GetClientData(self.mask2.GetSelection())
+
+        print op, m1.name, m2.name
+
+        Publisher.sendMessage('Do boolean operation', (op, m1, m2))
diff --git a/invesalius/gui/frame.py b/invesalius/gui/frame.py
index 24ab96c..f6f645c 100644
--- a/invesalius/gui/frame.py
+++ b/invesalius/gui/frame.py
@@ -397,6 +397,9 @@ class Frame(wx.Frame):
         elif id == wx.ID_REDO:
             self.OnRedo()
 
+        elif id == const.ID_BOOLEAN_MASK:
+            self.OnMaskBoolean()
+
     def OnSize(self, evt):
         """
         Refresh GUI when frame is resized.
@@ -490,10 +493,11 @@ class Frame(wx.Frame):
         Publisher.sendMessage('Redo edition')
 
 
+    def OnMaskBoolean(self):
+        print "Mask boolean"
+        Publisher.sendMessage('Show boolean dialog')
       
 
-
-
 # ------------------------------------------------------------------
 # ------------------------------------------------------------------
 # ------------------------------------------------------------------
@@ -605,6 +609,8 @@ class MenuBar(wx.MenuBar):
         #app(const.ID_EDIT_LIST, "Show Undo List...")
         #################################################################
 
+        file_edit.Append(const.ID_BOOLEAN_MASK, _(u"\tBoolean operations"))
+
 
         # VIEW
         #view_tool_menu = wx.Menu()
--
libgit2 0.21.2