diff --git a/lemon/adaptors.h b/lemon/adaptors.h
--- a/lemon/adaptors.h
+++ b/lemon/adaptors.h
@@ -360,6 +360,9 @@
   /// by adding or removing nodes or arcs, unless the \c GR template
   /// parameter is set to be \c const.
   ///
+  /// This class provides item counting in the same time as the adapted
+  /// digraph structure.
+  ///
   /// \tparam DGR The type of the adapted digraph.
   /// It must conform to the \ref concepts::Digraph "Digraph" concept.
   /// It can also be specified to be \c const.
@@ -719,6 +722,8 @@
   /// by adding or removing nodes or arcs, unless the \c GR template
   /// parameter is set to be \c const.
   ///
+  /// This class provides only linear time counting for nodes and arcs.
+  ///
   /// \tparam DGR The type of the adapted digraph.
   /// It must conform to the \ref concepts::Digraph "Digraph" concept.
   /// It can also be specified to be \c const.
@@ -1314,6 +1319,8 @@
   /// by adding or removing nodes or edges, unless the \c GR template
   /// parameter is set to be \c const.
   ///
+  /// This class provides only linear time counting for nodes, edges and arcs.
+  ///
   /// \tparam GR The type of the adapted graph.
   /// It must conform to the \ref concepts::Graph "Graph" concept.
   /// It can also be specified to be \c const.
@@ -1471,6 +1478,8 @@
   /// by adding or removing nodes or arcs/edges, unless the \c GR template
   /// parameter is set to be \c const.
   ///
+  /// This class provides only linear time item counting.
+  ///
   /// \tparam GR The type of the adapted digraph or graph.
   /// It must conform to the \ref concepts::Digraph "Digraph" concept
   /// or the \ref concepts::Graph "Graph" concept.
@@ -1619,6 +1628,8 @@
   /// by adding or removing nodes or arcs, unless the \c GR template
   /// parameter is set to be \c const.
   ///
+  /// This class provides only linear time counting for nodes and arcs.
+  ///
   /// \tparam DGR The type of the adapted digraph.
   /// It must conform to the \ref concepts::Digraph "Digraph" concept.
   /// It can also be specified to be \c const.
@@ -1729,6 +1740,8 @@
   /// by adding or removing nodes or edges, unless the \c GR template
   /// parameter is set to be \c const.
   ///
+  /// This class provides only linear time counting for nodes, edges and arcs.
+  ///
   /// \tparam GR The type of the adapted graph.
   /// It must conform to the \ref concepts::Graph "Graph" concept.
   /// It can also be specified to be \c const.
@@ -2232,6 +2245,9 @@
   /// by adding or removing nodes or edges, unless the \c GR template
   /// parameter is set to be \c const.
   ///
+  /// This class provides item counting in the same time as the adapted
+  /// digraph structure.
+  ///
   /// \tparam DGR The type of the adapted digraph.
   /// It must conform to the \ref concepts::Digraph "Digraph" concept.
   /// It can also be specified to be \c const.
@@ -2535,6 +2551,9 @@
   /// by adding or removing nodes or arcs, unless the \c GR template
   /// parameter is set to be \c const.
   ///
+  /// This class provides item counting in the same time as the adapted
+  /// graph structure.
+  ///
   /// \tparam GR The type of the adapted graph.
   /// It must conform to the \ref concepts::Graph "Graph" concept.
   /// It can also be specified to be \c const.
@@ -2678,6 +2697,8 @@
   /// arcs).
   /// This class conforms to the \ref concepts::Digraph "Digraph" concept.
   ///
+  /// This class provides only linear time counting for nodes and arcs.
+  ///
   /// \tparam DGR The type of the adapted digraph.
   /// It must conform to the \ref concepts::Digraph "Digraph" concept.
   /// It is implicitly \c const.
@@ -3325,6 +3346,9 @@
   /// costs/capacities of the original digraph to the \e bind \e arcs
   /// in the adaptor.
   ///
+  /// This class provides item counting in the same time as the adapted
+  /// digraph structure.
+  ///
   /// \tparam DGR The type of the adapted digraph.
   /// It must conform to the \ref concepts::Digraph "Digraph" concept.
   /// It is implicitly \c const.