Codeposition of metal chlorides with Pt colloidal nanoparticles on TiO2 followed by oxidation at 400 degrees C and reduction at 200 degrees C improved the activity for Pt-catalyzed CO oxidation with stoichiometric amount of O-2. The highest activity was obtained when FeCl3 was used as the additive with the Fe/Pt ratio of 0.2. XAFS, X-EDS, FTIR, and catalytic studies revealed that the deposition of Fe species on the reduced Pt sites gave active sites, which exhibited CO oxidation with high efficiency.