The adsorption of CO on (1 1 1), (1 1 0) surfaces of ceria (CeO2) was studied using projector-augmented wave (PAW) method based density-functional theory within generalized gradient approximation (GGA). It is found that there exist different adsorption features for CO on (1 1 1) and (1 1 0) surfaces. While only weak adsorptions are found on (1 1 1) surface, both weak and strong adsorptions exist on (1 1 0) surface. Electrostatic interactions were involved in the weak interactions, while covalent bonding was developed in the strong adsorptions. The strongly adsorbed CO on the (1 1 0) surface of CeO2 forms carbonate species as found in the IR experiments. (C) 2004 Elsveir B.V. All rights reserved.