A study has been conducted to identify the influence of zirconia phase and copper to zirconia surface area on the activity of Cu/ZrO2 catalysts for the synthesis of methanol from either CO/H-2 or CO2/H-2,. To determine the effects of zirconia phase, a pair of Cu/ZrO2, catalysts was prepared on tetragonal (t-) and monoclinic (m-) zirconia. The zirconia surface area and the Cu dispersion were essentially identical for these two catalysts. At 548 K, 0.65 MPa, and H-2/COx = 3 (x = 1, 2), the catalyst prepared on m-ZrO2 was 4.5 times more active for methanol synthesis from CO2/H-2 than that prepared on t-ZrO2, and 7.5 times more active when CO/H-2 was used as the feed. Increasing the surface area of m-ZrO2 and the ratio of Cu to ZrO2 surface areas further increased the methanol synthesis activity. In situ infrared spectroscopy and transient-response experiments indicate that the higher rate of methanol synthesis from CO2/H-2 over Cu/m-ZrO2 is due solely to the higher concentration of active intermediates. By contrast, the higher rate of methanol synthesis from CO/H-2, is due to both a higher concentration of surface intermediates and the more rapid dynamics of their transformation over Cu/ZiO(2).