A recent experimental result shows that Pt L-edge XANES spectra for Pt small cluster with similar to20 Pt atoms are sensitive to CO adsorption. In the present study we try to extract useful information about geometric and electronic structures of these cluster by applying a full multiple-scattering approach for the XANES analyses. Although IR analyses show that [CO](top)/[CO](bridge) is nearly constant for wide range of [Co](ad), it is difficult to estimate the ratio because of the large difference of the IR transition intensity for different adsorbed CO molecules. The present XANES analyses provide us useful new information [CO](top)/[CO](bridge) = 1-2. (C) 2002 Published by Elsevier Science B.V.