A commercial activated carbon (AC) was used as a catalyst support either in its original form or after two different oxidation treatments, namely air oxidation and HNO3 oxidation, aiming at the enhancement of its textural and surface chemical characteristics. These properties were determined by N-2 adsorption and temperature programmed desorption (TPD), respectively. Monometallic Pt and bimetallic Pt-Sn catalysts were prepared on the AC supports. Impregnation was used in the preparation of the monometallic samples. For the bimetallic samples, coimpregnation and a sequential impregnation procedure, in which the Sn precursor is introduced prior to Pt, were used. The Pt load was kept tired as 1 wt.% for all monometallic and bimetallic samples. Two different Sn loads, 0.25 and 0.50 wt.%, were used for the bimetallic samples in order to investigate the effects of Sn load on the catalytic properties. The catalyst samples were characterized by H-2 adsorption, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and structure insensitive benzene hydrogenation. The activities of all samples were measured in CO oxidation. The results indicate the strong effects of the surface chemistry of the AC supports; the Pt:Sn ratio, the preparation procedure and the reduction procedure, on the CO oxidation activities of the catalysts.