Gold supported on CeO2 nanocrystals of rod, cubic and polyhedral shapes were used for CO preferential oxidation (CO-PROX) in H-2-rich gas. The catalytic activity ranked by CeO2 nanocrystals as follows: rods > polyhedra > cubes. The results of X-ray photoelectron spectroscopy, temperature-programmed reduction/desorption and in situ Fourier transform infrared spectroscopy indicated that the surface gold species and also the adsorption/desorption properties for CO and oxygen species were closely related to the nature of exposed crystal planes of CeO2 nanocrystals. The gold catalyst on CeO2-rods with {1 0 0}/{1 1 0}-dominant surfaces showed the best CO-PROX performance. (C) 2009 Elsevier B.V. All rights reserved.