Carbon structures such as carbon nanofibers and activated carbon have enormous potential as novel support material for electrocatalysts such as platinum (Pt) used in fuel cell electrodes. However, chemical functionalization of their surface is necessary to deposit platinum. Usefulness of such a material requires that platinum particles be deposited very finely and homogeneously on the carbon surface. This in turn is dependent on a variety of factors prominently the nature of functionalized support and the experimental parameters involved in platinum deposition. We have employed the �colloidal' method of supported catalyst synthesis for homogeneous deposition of platinum catalyst on the functionalized carbon supports, under optimized preparation conditions. A relationship has been established between the variation in platinum particle size with nature of the chemically modified carbon surface, its surface treatment and processing variables. Electrochemical parameters such as the electrochemically active surface area of platinum on various carbons has been determined by cyclic voltammetry while rotating disk electrode studies have been carried out to determine activity of the supported platinum catalyst towards oxygen reduction. Membrane Electrode Assemblies (MEA) have been fabricated using the supported platinum electrodes and Nafion� membranes. Fuel cell performance for the MEAs is reported as current-potential polarization curves. An attempt is made to isolate and identify the effect of electrical conductivity of the carbon support, and microstructure of the carbon electrode on polarization response of the MEA.