diff -r 113e9c6fd64d Lib/tkinter/test/test_ttk/test_widgets.py
--- a/Lib/tkinter/test/test_ttk/test_widgets.py	Wed Feb 24 06:14:15 2016 +0000
+++ b/Lib/tkinter/test/test_ttk/test_widgets.py	Wed Feb 24 11:49:33 2016 +0200
@@ -1486,6 +1486,57 @@ class TreeviewTest(AbstractWidgetTest, u
             value)
 
 
+    def test_selection(self):
+        # item 'none' doesn't exist
+        self.assertRaises(tkinter.TclError, self.tv.selection_set, 'none')
+        self.assertRaises(tkinter.TclError, self.tv.selection_add, 'none')
+        self.assertRaises(tkinter.TclError, self.tv.selection_remove, 'none')
+        self.assertRaises(tkinter.TclError, self.tv.selection_toggle, 'none')
+
+        item1 = self.tv.insert('', 'end')
+        item2 = self.tv.insert('', 'end')
+        c1 = self.tv.insert(item1, 'end')
+        c2 = self.tv.insert(item1, 'end')
+        c3 = self.tv.insert(item1, 'end')
+        self.assertEqual(self.tv.selection(), ())
+
+        self.tv.selection_set((c1, item2))
+        self.assertEqual(self.tv.selection(), (c1, item2))
+        self.tv.selection_set(c2)
+        self.assertEqual(self.tv.selection(), (c2,))
+
+        self.tv.selection_add((c1, item2))
+        self.assertEqual(self.tv.selection(), (c1, c2, item2))
+        self.tv.selection_add(item1)
+        self.assertEqual(self.tv.selection(), (item1, c1, c2, item2))
+
+        self.tv.selection_remove((item1, c3))
+        self.assertEqual(self.tv.selection(), (c1, c2, item2))
+        self.tv.selection_remove(c2)
+        self.assertEqual(self.tv.selection(), (c1, item2))
+
+        self.tv.selection_toggle((c1, c3))
+        self.assertEqual(self.tv.selection(), (c3, item2))
+        self.tv.selection_toggle(item2)
+        self.assertEqual(self.tv.selection(), (c3,))
+
+        self.tv.insert('', 'end', id='with spaces')
+        self.tv.selection_set('with spaces')
+        self.assertEqual(self.tv.selection(), ('with spaces',))
+
+        self.tv.insert('', 'end', id='{brace')
+        self.tv.selection_set('{brace')
+        self.assertEqual(self.tv.selection(), ('{brace',))
+
+        self.tv.insert('', 'end', id='unicode\u20ac')
+        self.tv.selection_set('unicode\u20ac')
+        self.assertEqual(self.tv.selection(), ('unicode\u20ac',))
+
+        self.tv.insert('', 'end', id=b'bytes\xe2\x82\xac')
+        self.tv.selection_set(b'bytes\xe2\x82\xac')
+        self.assertEqual(self.tv.selection(), ('bytes\xe2\x82\xac',))
+
+
     def test_set(self):
         self.tv['columns'] = ['A', 'B']
         item = self.tv.insert('', 'end', values=['a', 'b'])
diff -r 113e9c6fd64d Lib/tkinter/ttk.py
--- a/Lib/tkinter/ttk.py	Wed Feb 24 06:14:15 2016 +0000
+++ b/Lib/tkinter/ttk.py	Wed Feb 24 11:49:33 2016 +0200
@@ -1396,7 +1396,9 @@ class Treeview(Widget, tkinter.XView, tk
 
     def selection(self, selop=None, items=None):
         """If selop is not specified, returns selected items."""
-        return self.tk.call(self._w, "selection", selop, items)
+        if isinstance(items, (str, bytes)):
+            items = (items,)
+        return self.tk.splitlist(self.tk.call(self._w, "selection", selop, items))
 
 
     def selection_set(self, items):