The monometallic silver supported on SiO2, Al2O3, ZSM-5 (Si:Al = 100) and bi-metallic AgCe/SiO2 samples were studied in the reaction of the preferential CO oxidation. It was established that the supported silver catalysts are promising systems for selective oxidation of CO at low temperatures and the addition of cerium oxide increases the catalytic activity and selectivity most probably because of the increase in the silver dispersion; the homogeneous distribution of Ag and ceria on the silica support; formation of Ag-n(delta+) clusters; increase in bulk and subsurface oxygen.