The selective CO oxidation reaction in H-2-rich gas mixture (COPROX) was investigated over microstructured reactors based on Cu/Al2O3 films deposited onto stainless steel microgrids. The catalytic activity results showed that these Cu/Al2O3 films were more active and selective to produce CO2 compared to the conventional catalysts in powder shape with the same copper loadings. The characterisation of the assayed catalysts in COPROX reaction demonstrated that their catalytic behavior was related to the copper species distribution. Hence, at low temperatures (<250 degrees C), the Cu/Al2O3 films were more active because of the exclusive presence of CuO clusters together with CuO interacting with the substrate. However, at high COPROX reaction temperatures (>250 degrees C), the presence of highly dispersed CuO on the alumina surface, in both series of the catalysts, which presented a re-oxidation capacity, led to similar catalytic behavior in terms of the CO conversion and the corresponding selectivity to produce CO2. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.