A semiconductor titania (TiO2) surface was modified by surfactant adsorption to make it more hydrophobic and to increase the adsorption of hydrophobic organic compounds (HOCs) and their photodegradation rates under UV irradiation. Photocatalytic experiments using TiO2 suspensions were conducted in the batch mode in a 10 ml reactor made of quartz, Two anionic surfactants, a hydrocarbon-based surfactant, sodium dodecylsulfate (SDS), and a fluorocarbon-based surfactant, potassium perfluorooctylsulfonate (PFOS), were used for titania surface modification, A hydrophobic organic compound namely, 1,2-dichlorobenzene (DCB), a chlorinated aromatic compound, was used as the test HOC. PFOS, which is resistant to UV irradiation, increased both the adsorption and photodegradation of DCB on titania. SIDS, however, competed for photodegradation and inhibited the degradation of PCB. VD 2001 Elsevier Science BN. All rights reserved.