Volatile organic compounds (VOCs) are prevalent components of indoor air pollution. The photocatalytic degradation could be an interesting method to degrade them. This paper reports the photoactivity study of two classical nano-sized and two micro-sized commercial TiO2 powdered samples. Photocatalytic tests have been performed following the degradation of acetone, acetaldehyde and toluene in the gas phase under UV light. An accurate study of the intermediate oxidation products was performed. XPS and FTIR analyses allowed to highlight the relationship between TiO2 surface properties and reactivity toward VOCs explaining the different behavior of the photocatalyst in case of hydrophilic and hydrophobic pollutants. (C) 2013 Elsevier B.V. All rights reserved.