Multi-walled carbon nanotubes (MWCNTs) based microporous layer on the non-woven carbon paper substrates was prepared by in situ growth in a chemical vapor deposition method. Pt with a loading of similar to 0.13 mg cm(-2) was electrodeposited at -0.3, -0.6, -1.2, -2.4, and -3.6 V vs SCE in a chloroplatinic acid (60 g/L) and hydrochloric acid (10 g/L) bath using a potentiostat. Scanning electron micrographs showed that the Pt nanoparticles decorated on the MWCNTs/carbon paper are highly uniform, especially at an electrodeposition. voltage of -0.6 V vs SCE. Pt particles' size at various deposition potentials, as estimated by X-ray diffraction analysis is in nanosize range with an average diameter of 6 nm. Fuel cell performance of the Pt deposited in situ grown MWCNTs carbon paper was evaluated using Nafion-212 membrane at various operating conditions. The cathode with Pt deposition at -0.6 V showed a power density of similar to 640 mW cm(-2) at 80 degrees C using H(2) and O(2) at 90% RH and 101 kPa. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.