In this paper the degradation of gaseous alcohols (methanol, ethanol, 1-propanol and 1-butanol) has been studied in a continuous reaction system. Methanol and ethanol, but not 1-propanol and 1-butanol, have caused the catalyst bare-TiO2 to become deactivated. The catalyst containing activated carbon, AC-TiO2, has not shown almost deactivation in any experiment. To explain this behaviour variation, a thorough FTIR study concerning the interaction of gaseous alcohols with the catalyst surface and the effect of light on the process was performed. Thus, the interaction of the different catalysts with the selected alcohols, the formed species and the hydroxyl group evolution under irradiation was studied. (C) 2004 Elsevier B.V. All rights reserved.