FT-IR spectroscopy and TPD profiles were performed to determine and compare the surface properties of amorphous, monoclinic and tetragonal zirconia polymorphs. It was found that zirconia polymorphs exhibited different surface hydroxyl and acid-base properties. These differences had great influence on the behavior of CO adsorption and reaction. Formate species could be formed at higher temperature via CO reaction with hydroxyl groups on the surface of amorphous and monoclinic zirconia, while bicarbonate and carbonate species were detected on tetragonal zirconia. whether hydrogen introduced or not. (C) 2004 Elsevier B.V. All rights reserved.