This study shows the effect of different titanium dioxides in transforming the structural properties of natural organic matter (NOM) during photocatalytic degradation with a solar UV light simulator. Titanium dioxide (TiO2) synthesized by the sol-gel method coupled with the solvothermal technique and Degussa P-25 TiO2 were used. The evolution of NOM degradation was followed by size exclusion chromatography with dissolved organic carbon, ultraviolet and fluorescence detection (SEC-DOC, SEC-UV254 and SEC-Fl(254/450)). For both catalysts, there was a preferential degradation of the larger molecules of NOM into medium and smaller molecular size fractions. However, the synthesized TiO2 was found to be more efficient than Degussa P-25 TiO2 for DOC removal, especially UV254 absorption and Fl(254/450) removal. (C) 2012 Elsevier B.V. All rights reserved.