Structural, electronic and magnetic properties of the small Con clusters (n = 2-7) endohedrally doped in C-60 (Ih) and C-82 (C2v) fullerenes were investigated using ab initio calculations based on the density functional theory. It is found that the encapsulated Co-n clusters inside C-60 and C-82 cages are energetically favorable except for Co-7@C-60. The encapsulation does not change significantly the structure of the enclosed clusters, but the magnetic moment of the clusters reduces due to a stronger Co-C hybridization for the larger clusters. (C) 2011 Elsevier B. V. All rights reserved.