The paper reports enhanced power densities for electrochemical capacitor through grafting carbon nanotubes (CNTs) onto the surface of activated carbon cloth (ACC). The surface-modified ACCs were first examined for their material properties and then evaluated for their electrode performance such as capacitance, equivalent series resistance, energy density, and power density. Improved electrochemical performance was obtained due to the surface modification by CNTs. In particular, the CNTs lower the contact resistance and therefore increase the power density of the electrochemical capacitor. Furthermore, we show that through such a surface modification, the specific capacitance can be increased from 108 to 117 F/g, i.e., an 8.3% increase, the energy density can be increased from 16.7 to 17.64 Wh/kg, i.e., a 5.4% increase, or the power density can be increased from 4.8 to 11.3 kW/kg, i.e., a 135% increase. To our best knowledge, the energy density and power density of a electrochemical capacitor having CNT-grafted ACC electrode have not been reported. Also, a 70% retention at a scan rate of 500 mV s-1 and a long cycle life of 20,000 cycles at a scan rate of 200 mV s-1 are demonstrated. 2013 Elsevier B.V. All rights reserved.