Density-functional calculations were done to examine the interface between graphene and a Pt-13 or Au-13 cluster. Introducing a carbon vacancy into a graphene sheet enhanced the interaction between graphene and the metal clusters. Five- or seven-member rings introduced into the graphene also increased the stability of the interface. The CO and H chemisorption energies on the metal clusters on graphene were calculated to clarify support-dependent reactivity. (c) 2006 Elsevier B.V. All rights reserved.