The oxidation of methanol was carried out on platinum nanoparticles supported-on carbon Vulcan (10 wt % Pt/C); as well as on the tungsten-oxide-modified material (Pt/WO3-C; WO3 5 wt %). The Pt/C samples were synthesized by the impregnation method, and the tungsten oxide was added by an in situ reflux approach. It was found, by using online.differential electrochemical mass spectrometry (DEMS), that the.route for methanol oxidation on the Pt/C surface is quite different from the Pt/WO3-C sample. When the support matrix is modified with tungsten-oxide species, the reaction pathway is also modified, producing some traces of formic acid and increasing the direct-methanol- oxidation toward CO2 (n/z = 44). HRTEM and X-ray photoelectron spectroscopy analysis showed the interaction between platinum and tungsten. This fact is associated with the redox process of WO3 to form hydrogen tungsten-oxide-bronzes or lower tungsten-oxide oxidation states, and it might explain the role of tungsten in the interfacial electrochemistry included in the W03-0H Pt complex.