This work reports the results of the studies on oxidation of carbon monoxide and H 2 over Pt supported on barium stannate (BaSnO 3 -perovskite type oxide). The composition and properties of Pt/BaSnO 3 catalysts were characterized by X-ray diffraction (XRD), time-of-flight secondary ion mass spectrometry (TOF-SIMS), H 2 and CO chemisorption, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and tested in the reactions of carbon monoxide and hydrogen oxidation. It was stated that platinum strongly interacts with BaSnO 3 . The catalytic activity and adsorption properties of Pt/BaSnO 3 catalysts are determined by these interactions. The presence of different species (which generally can be labelled as [(Pt)BaSnO 3 ]) resulting from platinum and BaSnO 3 chemical interaction was found by the TOF-SIMS on surface of Pt/BaSnO 3 catalysts. The mechanism of CO and H 2 oxidation over Pt/BaSnO 3 catalysts was discussed in the light of strong interactions between Pt and BaSnO 3 .