The relationship between the structure-specific capacitance (Fg−1) of a composite electrode consisting of activated coconut-shell carbon and hydrous ruthenium oxide (RuO x (OH) y ) has been evaluated by impregnating various amounts of RuO x (OH) y into activated carbon that is specially prepared with optimum pore-size distribution. The composite electrode shows an enhanced specific capacitance of 250Fg−1 in 1M H2SO4 with 9wt.% ruthenium incorporated. Chemical and structural characterization of the composites reveals a homogeneous distribution of amorphous RuO x (OH) y throughout the porous network of the activated carbon. Electrochemical characterization indicates an almost linear dependence of capacitance on the amount of ruthenium owing to its pseudocapacitive nature.