Ru catalysts supported on different mesoporous silicas, MCM-41, MCM-48, SBA-15 and KIT-6, were applied to the preferential oxidation of CO in a H-2-rich atmosphere (PROX). The properties of mesoporous support and the supported Ru catalysts were investigated using N-2 physisorption, FTIR, TEM. CO chemisorption, H-2-TPR and XPS. The performance of Ru catalysts in PROX highly relates to the Ru dispersion, support pore structure, Ru reducibility and the interaction between Ru and support. Ru/KIT-6 presents the highest surface activity (TOF values), owing to the easiest reducibility of Ru. Nevertheless, its poor Ru dispersion results in a low number of surface active sites, leading to the low CO conversion value over Ru/KIT-6. Ru/MCM-41 can achieve full CO conversion and the high CO2 selectivity in the reaction temperature range of 115-180 degrees C owing to the high Ru dispersion from the strong interaction between Ru and MCM-41. (C) 2012 Elsevier B.V. All rights reserved.