Multi-walled carbon nanotubes (CNTs)were chemically activated using KOH in order to improve their specific surface area, electrical conductivity, and specific capacitance. Using such an activated CNT (A-CNT), a composite of MnO2/A-CNT was prepared by the coprecipitation method, and its physical and electrochemical properties were evaluated for use as an electrode material in supercapacitors. For comparison, a composite of MnO2/CNT was also prepared using an inactivated CNT and characterized in an aqueous solution of 1.0 M Na2SO4. The specific capacitances of the MnO2/A-CNT composite electrode, measured using cyclic voltammetry at scan rates of 10 and 100 mV s(-1), were found to be 250 and 184 Fg(-1), respectively, compared to 215 and 138 Fg(-1), respectively, for the MnO2/CNT composite electrode. Because of CNT activation, the MnO2/A-CNT composite electrode showed an improved performance in both the capacitance and cycle performance, due to the alleviation of the accumulated stress during charge-discharge cycling. (C) 2008 Elsevier B.V. All rights reserved.