The electrochemical behavior of thermally prepared ruthenium oxide films, including pH influence, electrolyte dependence and counter-ion identification, was studied using cyclic voltammetry and mirage (probe beam deflection : PBD) technique. Results are compared to those previously obtained with sputtered iridium oxide since both oxides are electrochemical "supercapacitor" materials. In contrast with sputtered iridium oxide, the voltammogram shape of thermally prepared ruthenium oxide films does not depend on the electrolyte type. This is tentatively correlated with the nature of the counter-ion exchanged with the electrolyte.