The electrochemical properties of doped diamond electrodes (10(17)-10(19) B cm(-3)) grown on carbon fiber cloths in H2SO4 0.1 mol L-1 electrolyte were investigated. Cyclic voltammograms of B-doped diamond/carbon fiber cloth and carbon fiber cloth electrodes showed that both kinds of electrodes possess similar working potential windows of about 2.0 V The electrode capacitance was determined by impedance spectroscopy and chronopotentiometry measurements and very close values were obtained. The capacitance values of the diamond film on carbon fiber cloths were 180 times higher than the ones of diamond films on Si. In this paper we have also discussed the capacitance frequency dependence of diamond/carbon cloth electrodes. (C) 2007 Elsevier B.V. All rights reserved.