Environmentally relevant polar persistent organic pollutants (pharmaceuticals and diagnostic agents) were chosen according to human consumption and occurrence in the aquatic environment (sewage plant effluents, rivers and groundwater) to investigate their behavior during photocatalytic oxidation. From data compilation in the literature, the active metabolite clofibric acid of some lipid lowering agents, the anti-epileptic drug carbamazepine and the X-ray contrast media iomeprol were selected. The degradation of the persistent pollutant was monitored by HPLC/DAD/FLD. The study also focuses on the identification and quantification of possible degradation products by HPLC/DAD/FLD and HPLC/MS/MS. The degradation process was also monitored by determination of sum parameters and inorganic ions. Various aromatic and aliphatic degradation products have been identified and quantified. From analytical data, a possible degradation scheme for carbamazepine was proposed. Kinetic studies showed that the TiO2 photocatalyst P25 was more active in clofibric acid degradation than Hombikat UV 100. For photocatalytic degradation of iomeprol Hombikat UV 100 was more suitable than P25. In general the presence of NOM and carbamazepine retarded the photocatalysis of clofibric acid. Radiation attenuation, competition for active sites and surface deactivation of the catalyst by adsorption are the reason for that. The results of this work proof that photocatalysis is a promising technology to reduce persistent substances even if they are present in low concentrations or in a complex matrix. © 2005 Published by Elsevier B.V.