diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7eb6d84b..968cffb9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ CHANGELOG for FlatCAM beta
 
 - Tool Drilling - working on the UI
 - Tool Drilling - added more tool parameters; laying the ground for adding "Drilling Slots" feature
+- added as ToolTip for the the Preprocessor combobox items, the actual name of the items
 
 7.07.2020
 
diff --git a/appObjects/FlatCAMGeometry.py b/appObjects/FlatCAMGeometry.py
index 11cee268..2d5b089a 100644
--- a/appObjects/FlatCAMGeometry.py
+++ b/appObjects/FlatCAMGeometry.py
@@ -399,9 +399,15 @@ class GeometryObject(FlatCAMObj, Geometry):
         self.units = self.app.defaults['units'].upper()
         self.units_found = self.app.defaults['units']
 
+        # make sure the preprocessor combobox is clear
+        self.ui.pp_geometry_name_cb.clear()
         # populate preprocessor names in the combobox
         for name in list(self.app.preprocessors.keys()):
             self.ui.pp_geometry_name_cb.addItem(name)
+        # add tooltips
+        for it in range(self.ui.pp_geometry_name_cb.count()):
+            self.ui.pp_geometry_name_cb.setItemData(
+                it, self.ui.pp_geometry_name_cb.itemText(it), QtCore.Qt.ToolTipRole)
 
         self.form_fields.update({
             "plot": self.ui.plot_cb,
diff --git a/appTools/ToolDrilling.py b/appTools/ToolDrilling.py
index 93e728f8..380329e0 100644
--- a/appTools/ToolDrilling.py
+++ b/appTools/ToolDrilling.py
@@ -242,12 +242,18 @@ class ToolDrilling(AppTool, Excellon):
         except Exception:
             pass
 
+        # reset the Excellon preprocessor combo
+        self.t_ui.pp_excellon_name_cb.clear()
         # populate Excellon preprocessor combobox list
         for name in list(self.app.preprocessors.keys()):
             # the HPGL preprocessor is only for Geometry not for Excellon job therefore don't add it
             if name == 'hpgl':
                 continue
             self.t_ui.pp_excellon_name_cb.addItem(name)
+        # add tooltips
+        for it in range(self.t_ui.pp_excellon_name_cb.count()):
+            self.t_ui.pp_excellon_name_cb.setItemData(
+                it, self.t_ui.pp_excellon_name_cb.itemText(it), QtCore.Qt.ToolTipRole)
 
         # update the changes in UI depending on the selected preprocessor in Preferences
         # after this moment all the changes in the Posprocessor combo will be handled by the activated signal of the
diff --git a/app_Main.py b/app_Main.py
index d4485745..66922dbe 100644
--- a/app_Main.py
+++ b/app_Main.py
@@ -561,6 +561,7 @@ class App(QtCore.QObject):
             # and now put back the ordered dict with 'default' key first
             self.preprocessors = new_ppp_dict
 
+        # populate the Preprocessor ComboBoxes in the PREFERENCES
         for name in list(self.preprocessors.keys()):
             # 'Paste' preprocessors are to be used only in the Solder Paste Dispensing Tool
             if name.partition('_')[0] == 'Paste':
@@ -574,6 +575,19 @@ class App(QtCore.QObject):
 
             self.ui.excellon_defaults_form.excellon_opt_group.pp_excellon_name_cb.addItem(name)
 
+        # add ToolTips for the Preprocessor ComboBoxes in Preferences
+        for it in range(self.ui.tools_defaults_form.tools_solderpaste_group.pp_combo.count()):
+            self.ui.tools_defaults_form.tools_solderpaste_group.pp_combo.setItemData(
+                it, self.ui.tools_defaults_form.tools_solderpaste_group.pp_combo.itemText(it), QtCore.Qt.ToolTipRole)
+        for it in range(self.ui.geometry_defaults_form.geometry_opt_group.pp_geometry_name_cb.count()):
+            self.ui.geometry_defaults_form.geometry_opt_group.pp_geometry_name_cb.setItemData(
+                it, self.ui.geometry_defaults_form.geometry_opt_group.pp_geometry_name_cb.itemText(it),
+                QtCore.Qt.ToolTipRole)
+        for it in range(self.ui.excellon_defaults_form.excellon_opt_group.pp_excellon_name_cb.count()):
+            self.ui.excellon_defaults_form.excellon_opt_group.pp_excellon_name_cb.setItemData(
+                it, self.ui.excellon_defaults_form.excellon_opt_group.pp_excellon_name_cb.itemText(it),
+                QtCore.Qt.ToolTipRole)
+
         # ###########################################################################################################
         # ##################################### UPDATE PREFERENCES GUI FORMS ########################################
         # ###########################################################################################################