Hydrous ruthenium-oxide (RuOxHy) particles composed of nanocrystallites of similar to 5 nm in size were prepared, using hexagonal self-ordered mesoporous SiO2 (SBA-15) as a template and RuCl3 as the ruthenium precursor. The material has a highly mesoporous structure with a sharp distribution of fine pores of size around 3-4 nm. A high specific capacitance of 954 F g(-1) for the RuOxHy in 1M H2SO4(aq) and a high energy density of 118.9 J g(-1) (or 32.7W h kg(-1)) were obtained from an electrochemical capacitor made with the material. Rectangular shape of the cyclic voltammetry was observed even increasing the scan rate to about 100 mV s(-1). (C) 2009 Published by Elsevier B.V.