The origin of carbon deposits arising in the CO hydrogenation process over Co/support catalysts, where the support is gamma-Al2O3, 0.5% MgO/gamma-Al2O3, or ZrO2 + 6% Y2O3, was studied by the temperature-programmed surface reaction method. It was shown that the catalyst nature influences the composition of the carbon deposits and their amount on the catalyst surface. The promotion of gamma-Al2O3 with magnesium ions and the hydrothermal. treatment of ZrO2 + 6% Y2O3 decrease the rate of catalyst carburization.