A quantum modeling of the CO adsorption on illuminated anatase TiO2 (0 0 1) is presented. The calculated adsorption energy and geometries of illuminated case are compared with the ground state case. The calculations were achieved by using DFT formalism and the BH and HLYP. Upon photoexcitation, an electron-hole pair is generated. Comparing of natural population in the ground state and the exited state, shows that an electron is trapped in a Ti4+ ion and a hole is localized in an oxygen ion. The photoelectron helps generation of a CO2 molecule on the TiO2 surface. As shown by optimization of these systems, the CO molecule adsorbed vertically on the TiO2 (0 0 1) surface in the ground state case while the CO moleculemade an angle of 134.3 degrees to this surface at the excited state case. Based on the here used model the obtained adsorption energy was 0.36 eV which is in excellent agreement with the reported experimental value. In the present work the C-O stretch IR frequencies are calculated which are 1366.53 and 1423.16 cm (1). These results are in good agreement with the earlier reported works for the surface carbonaceous compounds, and oxygenated carbon species. (C) 2010 Elsevier B.V. All rights reserved.