Similar to conventional composite electrodes, developing binderless-based carbon nano-structured (CNs) electrodes for fuel cells requires particularly the optimisation of both the morphology and the density of the CNs. In this work, carbon nanofibers (CNFs) have been optimised and used as catalyst support for Pt nanoparticles (NPs). The nontrivial role of the CNFs on the catalytic behavior is clearly demonstrated. We have shown that for a similar amount, morphology and dispersion of the Pt NPs fabricated onto CNFs, the density of the latter and to a lesser extent their diameter are the main factors influencing the catalytic activity. For the particular case of CNFs considered in this work, an optimum activity toward methanol fuel cell reaction was obtained when Pt NPs were supported with CNFs synthesized with a C2H2/Ar ratio of 0.31. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.