Electrochemical characteristics of lithium ruthenate (Li(x)RuO(2+0.5x)(.)nH(2)O) for electrochemical capacitors' electrode material were first examined in this paper by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge tests. Results show that Li(x)RuO(2+0.5x)(.)nH(2)O has electrochemical capacitive characteristic within the potential range of -0.2-0.9 V (vs. SCE) in 1 M Li2SO4 solution. The capacitance mainly arises from pseudo-capacitance caused by lithium ions' insertion/extraction into/out of the LixRuO(2+0.5x)(.)nH(2)O electrode. The specific capacitance of 391 F g(-1) can be delivered at 1 mA charge-discharge current for Li(x)RuO(2+0.5x)(.)nH(2)O electrode with an energy density of 65.7 W h kg(-1). This material also exhibits an excellent cycling performance and there is no attenuation of capacitance over 600 cycles. (c) 2006 Elsevier B.V. All rights reserved.