Voltammetric properties of electrodes made of multiple-walled carbon nanotubes (MWNTs) with different diameters were investigated by cyclic voltammetry. The results indicate that electrodes made of smaller MWNTs exhibit better voltammetric properties. In addition, electrodes made of mixed MWNTs with large diameter distribution possess the best voltammetric properties. The phenomenon can be explained by the filled-in frame structures formed on the electrode surface. (c) 2005 Elsevier B.V. All rights reserved.