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Homogeneous and well-adhered alumina washcoat was deposited onto stainless steel microgrids. Alumina-washcoated stainless steel microgrids loaded with different amounts of copper were synthesised and characterised by several techniques including SEM-EDS, N2 adsorption at -196 °C, XRD, temperature programmed reduction (H2-TPR), UV-visible-NIR DRS and XPS spectroscopy. Three types of copper species were detected in the series of the prepared microreactors: (i) CuO deposited on the surface of the substrate; (ii) highly dispersed CuO on the alumina surface and (iii) bulk CuO. As proven by H2-TPR experiments, the distribution of CuO between these three sites depended on copper loading. The prepared microreactors were successfully tested in CO oxidation reaction and compared to powder catalysts loaded with the same amount of copper. The results showed that the microstructured catalysts were more active than the powder catalysts when activated under reaction gas mixture. Indeed, a second catalytic run, performed on the same catalyst, revealed a decrease of the light-off temperature in the case of the prepared microreactors as result of their activation. The Cu species distribution seemed to play a decisive role in the activity of the microreactors. The CuO interacting with the substrate seemed to enhance the thermal conductivity of the microreactor and, thus, might better dissipate the heat generated, in the Cu/Al2O3 film, by the exothermic CO oxidation reaction. These catalytic features evidenced the potential of these microreactors as a promising alternative catalyst in the CO oxidation reaction. [ABSTRACT FROM AUTHOR]