Vapor-phase catalytic reactions of several reactants were investigated over CeO2 with different particle sizes, and the surface-structure sensitivity, i.e. crystal plane dependency, was discussed. The particle size of CeO2 was regulated by the calcination temperature. In.dehydration of 1,4-butanediol and 1,3-butanediol into unsaturated alcohols, and ketonization of propanoic acid, the activities increased with increasing the CeO2 particle size. CeO2 {111} facets became predominant on the large particles. This indicates that CeO2 {111} facets have active sites for the reactions of butanediols and of propanoic acid. Therefore, dehydration of 1,4-butanediol and 1,3-butanediol, and ketonization of propanoic acid are categorized into surface-structure-sensitive reaction. The structure-sensitive reactions have feature that the main product is formed with high selectivity at temperatures lower than 400 degrees C. In contrast, activities of dehydration of 2-heptanol, methylation of phenol with methanol, and ketonization of propanal and 1-propanol were independent of the CeO2 particle size. These reactions are categorized into structure-insensitive reaction. (c) 2007 Elsevier B.V. All rights reserved.