Tin-promoted bifunctional Cu-Zn-Al/HZSM-5 catalysts were prepared in order to increase the selectivity of carbon monoxide hydrogenation to dimethyl ether (DME). The catalysts were characterized by H-2-TPR, in-situ XRD, XPS, in-situ XANES and FTIR. The characterization revealed that the electronic properties and surface distribution of Cu in the catalysts were significantly changed by tin addition leading to the decrease in the fraction of ionic Cu species (Cu+ and Cu2+) and positively charged metallic Cu delta+ sites. Addition of tin suppressed the water gas shift reaction and decreased the selectivity to undesirable CO2. As a result, the selectivity to valuable DME and methanol increased for the mildly promoted catalysts. Further increase in Sn loading led to the decrease in the overall rate of carbon monoxide conversion. (C) 2015 Elsevier B.V. All rights reserved.