The redox-active films, C-60/Pd, formed by electrochemical reduction of solutions containing palladium(II) acetate and C-60 fullerene have been studied as active components for electrochemical capacitors. The capacitance properties of these materials have been investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The structure and electrochemical properties of films deposited on an electrode surface depend on the composition of the solution from which they are grown. Films formed in a solution with a low concentration of palladium(II) acetate exhibit conductivity in the potential range of the film reduction. The faradaic process of C-60 reduction gives rise to pseudocapacitance. The capacitance of this polymer depends on the solvent and the size of the cations in the supporting electrolyte. For an acetonitrile solution containing only tetra(methyl)ammonium perchlorate, the film displays a high specific capacitance, close to 300 F/g. Films formed in a solution with a high concentration of palladium(II) acetate also contain metallic palladium nanoparticles. Such systems exhibit conductivity at potentials less negative than the potentials for film reduction, and these films can be considered as double-layer capacitors. The specific capacitance of these films is much smaller (about 20 F/g) but a large potential window (from +800 to -2000 mV) is available for the performance of these capacitors. (c) 2007 The Electrochemical Society.