A detailed procedure for comparing high surface Pt/C catalysts was pointed out. Platinum dispersed carbon was prepared from carbonaceous material and chloroplatinic acid solution using sodium formiate. The real platinum metal surface area was evaluated by cyclic voltammetry on a thin porous coated disk electrode. The performance of catalysts prepared in our laboratory were similar to those of a well-known commercial one. The results show that electrochemical active surface (EAS) measurement is strongly influenced by the gas diffusion electrode (GDE) preparative method. It is only by means of a well-defined preparative procedure and data analysis that it is possible to use this technique to compare different carbon supported platinum catalysts.