CO adsorption and desorption, as studied by IR spectroscopy and mass spectrometry has been used to characterize PtNaY and PtxSnyNaY samples. The change observed between adsorbed CO spectra and CO TPD has been attributed to an increase of the particle sizes due to the addition of Sn to Pt. The catalytic properties of these materials were studied by using propane dehydrogenation and propane hydrogenolysis. The TOF of propene formation is nearly the same for all samples and the apparent activation energy remains unchanged, indicating that no change in the Pt dehydrogenation properties is induced by adding Sn. In contrast the hydrogenolysis properties are deeply depressed by alloying Pt to Sn, these changes being attributed to a dilution effect rather than to an electronic effect.