The effect of various modifiers on the performance of a commercial Cu/ZnO/Al2O3 catalyst in methanol synthesis from CO2/H-2 and CO/H-2 at 523 K and 30 bar has been studied. several modifiers improved significantly the rate of methanol formation from CO2/H-2, while all modified catalysts showed decreased rates for the synthesis from CO/H-2 in comparison with the unmodified Cu/ZnO/Al2O2 catalyst. The synthesis rates from both CO2/H-2 and CO/H-2 correlated with the oxygen coverage of copper surface measured after the reaction by N2O titration