diff --git a/examples/advanced.py b/examples/advanced.py
index 491bbb7..a57bb6c 100644
--- a/examples/advanced.py
+++ b/examples/advanced.py
@@ -43,11 +43,17 @@ def create_datalist_example():
             ]
     return test
     
-def create_datagroup_example():
+def create_combogroup_example():
     datalist = create_datalist_example()
-    return ((datalist, "Category 1", "Category 1 comment"),
+    return [(datalist, "Category 1", "Category 1 comment"),
             (datalist, "Category 2", "Category 2 comment"),
-            (datalist, "Category 3", "Category 3 comment"))
+            (datalist, "Category 3", "Category 3 comment")]
+
+def create_tabgroup_example():
+    datalist = create_datalist_example()
+    return ((datalist, "Title 1", "Title 1 comment"),
+            (datalist, "Title 2", "Title 2 comment"),
+            (datalist, "Title 3", "Title 3 comment"))
 
 def apply_function(result, widgets):
     print('result:', result)
@@ -83,14 +89,48 @@ def second_function(result, widgets):
                        type='questions',
                        scrollbar=True))
 
-#--------- datagroup example
-datagroup = create_datagroup_example()
+#--------- datagroup examples
+datagroup = create_combogroup_example()
 print("result:", fedit(datagroup, "Global title", result='JSON'))
 
-#--------- datagroup inside a datagroup example
+datagroup = create_tabgroup_example()
+print("result:", fedit(datagroup, "Global title", result='JSON'))
+
+#--------- datagroup inside a datagroup examples
+datalist = create_datalist_example()
+datagroup = create_tabgroup_example()
+print("result:", fedit([(datagroup, "Category 1", "Category 1 comment"),
+                        (datalist, "Category 2", "Category 2 comment"),
+                        (datalist, "Category 3", "Category 3 comment")],
+                        "Global title", result='XML'))
+
 datalist = create_datalist_example()
-datagroup = create_datagroup_example()
+datagroup = create_combogroup_example()
 print("result:", fedit(((datagroup, "Title 1", "Tab 1 comment"),
                         (datalist, "Title 2", "Tab 2 comment"),
                         (datalist, "Title 3", "Tab 3 comment")),
                         "Global title", result='XML'))
+
+datalist = create_datalist_example()
+datagroup = create_combogroup_example()
+print("result:", fedit([(datagroup, "Category 1", "Category 1 comment"),
+                        (datalist, "Category 2", "Category 2 comment"),
+                        (datalist, "Category 3", "Category 3 comment")],
+                        "Global title", result='XML'))
+
+datalist = create_datalist_example()
+datagroup = create_tabgroup_example()
+print("result:", fedit(((datagroup, "Title 1", "Tab 1 comment"),
+                        (datalist, "Title 2", "Tab 2 comment"),
+                        (datalist, "Title 3", "Tab 3 comment")),
+                        "Global title", result='XML'))
+
+datalist = create_datalist_example()
+datagroup = create_tabgroup_example()
+print("result:", fedit((([(datagroup, "Category 1", "Category 1 comment"),
+                          (datalist, "Category 2", "Category 2 comment"),
+                          (datalist, "Category 3", "Category 3 comment")],
+                          "Three", "Three levels"),
+                        (datagroup, "Two", "Two levels"),
+                        (datalist, "One", "One level")),
+                        "Global title", result='XML'))
diff --git a/formlayout.py b/formlayout.py
index 30391ab..35de4a3 100644
--- a/formlayout.py
+++ b/formlayout.py
@@ -779,7 +779,12 @@ def __init__(self, datalist, comment="", parent=None):
         self.widgetlist = []
         for data, title, comment in datalist:
             self.combobox.addItem(title)
-            widget = FormWidget(data, comment=comment, parent=self)
+            if isinstance(data, tuple) and len(data[0]) == 3:
+                widget = FormTabWidget(data, comment=comment, parent=self)
+            elif isinstance(data, list) and len(data[0]) == 3:
+                widget = FormComboWidget(data, comment=comment, parent=self)
+            else:
+                widget = FormWidget(data, comment=comment, parent=self)
             self.stackwidget.addWidget(widget)
             self.widgetlist.append((title, widget))
             
@@ -832,7 +837,9 @@ def __init__(self, datalist, comment="", parent=None):
         self.type = parent.type
         self.widgetlist = []
         for data, title, comment in datalist:
-            if len(data[0])==3:
+            if isinstance(data, tuple) and len(data[0]) == 3:
+                widget = FormTabWidget(data, comment=comment, parent=self)
+            elif isinstance(data, list) and len(data[0]) == 3:
                 widget = FormComboWidget(data, comment=comment, parent=self)
             else:
                 widget = FormWidget(data, comment=comment, parent=self)
@@ -917,10 +924,10 @@ def __init__(self, data, title="", comment="", icon=None, parent=None,
             import xml.etree.ElementTree as ET
 
         # Form
-        if isinstance(data[0][0], (list, tuple)):
+        if isinstance(data, tuple) and len(data[0]) == 3:
             self.formwidget = FormTabWidget(data, comment=comment,
                                             parent=self)
-        elif len(data[0])==3:
+        elif isinstance(data, list) and len(data[0]) == 3:
             self.formwidget = FormComboWidget(data, comment=comment,
                                               parent=self)
         else: