The effect of operating conditions (time on stream, temperature, pressure and space time) on the conversion of CO and CO2, selectivity to dimethyl ether (DME), yield of DME and product distribution is studied in the DME synthesis from H-2, CO and CO2 in a single reaction step on a CuO-ZnO-Al2O3/NaHZSM-5 bifunctional catalyst. CO conversion is total at 275 degrees C and 40 bar, with a selectivity to DME of 80% and a yield of DME of 78%, for a space time of 67 (g of catalyst) h/mol of (H-2 + CO) and for a feed made up of H-2/CO = 2/1. Catalyst deactivation under these conditions is insignificant, even when CO2 is fed and there is a high water concentration in the medium. (c) 2005 Elsevier B.V. All rights reserved.