ABSTRACT Silver-cobalt and silver-manganese composite oxides were prepared by co-precipitation method at different metal/metal oxide molar ratio and by different rates of preparation. The catalysts were characterised by X-Ray diffraction, BET and TGA. The CO oxidation studies were carried out in a micro reactor and reaction was formed under dry and wet atmospheres for a binary CO + air and CO + CO2  H2O + air gas mixtures. 1:1 Ag/Co prepared by the slow precipitation and 1:1 Ag/Mn prepared by the opposite slow precipitation gave the best performance for the dry conditions. Activity of these catalysts significantly decreased when the water vapor and CO2 was added to the feed. Silver-cobalt composite oxide catalyst shows a higher performance than the silver-manganese composite oxide catalyst for the wet atmospheres.  Keywords: CO oxidation, catalyst, co-precipitation, low-temperature