Supported Cu catalysts are widely used in the chemical industry. Here, we discuss the role of the Cu particle size in the hydrogenation of ethyl acetate, as a model reaction for Cu-based hydrogenation catalysis and a crucial step to produce ethanol via synthesis gas. A series of carbon-supported Cu catalysts was prepared with Cu particle sizes tuned between 3 and 14 nm. At temperatures of 180-210 degrees C and a pressure of 30 bar, the surface-normalized activity increased around 4-fold when increasing the Cu particle size from 3 to 10 nm, while it became constant for Cu particles above 10 nm, hence showing that the Cu-catalyzed hydrogenation reaction is weakly sensitive to the Cu surface structure. The apparent activation energy for the reaction was around 94 kJ mol(-1) for all Cu particle sizes, suggesting a size-independent nature of the active sites, whereas the abundance of the active sites increased with increasing Cu particle size below 10 nm. A maximal copper-normalized activity was achieved with Cu particles of around 6 nm, providing an optimal balance between intrinsic activity and available surface area. These findings may guide optimization strategies for reactions where hydrogenation of relatively stable intermediates is the rate-limiting step. (C) 2020 The Author(s). Published by Elsevier Inc.