The Pt catalysts supported on ceria-zirconia support with the Ce/Zr ratio of 1/3 (Pt/CZ(1/3)) were prepared. The catalytic activities of CO oxidation over Pt/CZ were investigated and compared with that over Pt/Al2O3. The CO oxidation reaction on Pt/CZ catalysts initiated at ca. 50 degrees C with no relation to the platinum loadings. From the estimation of activation energies and TOF, it appeared that the role of platinum particles was similar in Pt/CZ catalysts with the different platinum loadings. On the other hand, in Pt/CZ catalysts with the small platinum loadings, the platinum particles highly dispersed on the surface of CZ support. In addition, it was confirmed that the dispersion of platinum particles in Pt/CZ was higher than that in Pt/Al2O3. TPR measurements revealed that oxygen storage capacity (OSC) of CZ support enhanced the CO oxidation reaction. These results suggested that highly dispersed platinum particles and the oxygen storage capacity of CZ contributed to the high catalytic activities of CO oxidation. (C) 2012 Elsevier B. V. All rights reserved.