Platinum particles dispersed in a poly(2-hydroxy-3-aminophenazine) film (pHAPh/Pt) provide a better catalyst than smooth Pt for the electrooxidation of methanol and formic acid in perchloric acid aqueous solutions. The catalytic activity of the Pt particles is further enhanced when Sn is codeposited in the polymer film. In the case of formic acid oxidation, the activity of Pt nanoparticles is influenced by adatoms of Tl, Pb and Bi deposited undepotential conditions. The upd-modified Pt particles are much more active than bare Pt particles. The morphology and identity of the metallic dispersion were examined by transmission electron microscopy.