The heterogeneous photoassisted oxidation of cumene in liquid acetonitrile-oxygenated dispersions containing TiO2 catalyst has been studied in a photochemical reactor radiating predominantly at 365-366 nm. Acetophenone and CO2 have been detected as sole products. Particular attention is focused on the extent of cumene adsorption on the catalyst particle and its relation with the mechanistic features of cumene oxidation. A mechanism invoking methyl instead of phenyl migration, as observed in the thermal catalytic reaction, is proposed.