We present a DFT study for the adsorption of single Pt atom and Pt clusters on graphene surface and carbon nanotube. Adsorption of a Pt atom shows a heavy dependence of binding energy on the graphene curvature. The adsorbed Pt atoms tend to form clusters, than to disperse on the graphene surface. The Pt-Pt bond length and the charge transfer from Pt clusters to the nanotube vary as a function of cluster size. A simulation of oxygen adsorption suggests higher performance for catalytic activities of Pt clusters adsorbed on the nanotube, in comparison with free Pt clusters. (c) 2006 Elsevier B.V. All rights reserved.