The ground state structures of Co/Cu and Co/Pt clusters are obtained by empirical genetic algorithm, and further optimized using the density functional theory with generalized gradient approximation. For Co-13, Pt-13 and Cu-13, they show perfect I-h symmetry. The structures of bimetallic clusters are slightly distorted configuration of Co-13. The average magnetic moment of Co-13 is 2.38 μ(B)/atom, and that of Cu-13 and Pt-13 is nonzero. The local moments of the central atom are smaller than that of the surface ones for Co-13 and Cu-13. But the cases are not held for Pt-13. The total magnetic moment of clusters Co/Pt monotonously decreases with increasing the concentration of Pt atoms. But the things are much more complicated for clusters Co/Cu, and the reasons are discussed in detail. © 2005 Elsevier B.V. All rights reserved.