The effect of the functionalization degree of multi-walled carbon nanotubes (MWCNTs) on the synthesis and catalytic performance of Pt/MWCNT has been studied. In order to create surface groups of different strengths. MWCNTs have been subjected to either severe or mild oxidation treatment. The experimental data show that increasing metal dispersion is favored on severely treated nanotubes. This is because the treatment provides nucleating sites and enhances the hydrophilicity of the carbon surface. The Pt nanoparticles supported on the MWCNTs subjected to the most severe functionalization treatment gives the best cathode electrode for PEMFC applications, even exceeding the performance of commercial Pt/C. This is due to the higher dispersion of the Pt nanoparticles, as well as a smaller particle size, which is more appropriate for the oxygen reduction reaction. (C) 2010 Elsevier B.V. All rights reserved.