CO adsorptions on six model Pt nanoclusters were studied using the B3LYP, BMK and M05-2X methods. BMK and M05-2X gave a better unbound description of CO 2 pi* LUMO. The B3LYP results show no observable preference as reported earlier in other calculations. For BMK, the CO prefers to adsorb on top site except for Pt10-6-3 and Pt9-9-9. For M05-2X, top-site preference exists in the two-layer Pt10-6, Pt19-12 and the three-layer Pt9-9-9, but does not exist in other three-layer Pt clusters. Although BMK and M05-2X give the better LUMO of CO molecule, the poor description of the Pt band gap may cause problems in the site preference when the size increases. (C) 2010 Elsevier B.V. All rights reserved.