TiO2 supported ceria catalysts with 20 wt% CeO2 were prepared by impregnating rutile and anatase polymorphs in aqueous solution of ammonium ceric nitrate [(NH4)(2)Ce(NO3)(6)], characterized by BET surface area measurement and low temperature oxygen chemisorption (LTOC) at - 78 degrees C and evaluated for ammoxidation of beta- and gamma-picolines. Anatase supported catalyst has exhibited higher ammoxidation activities than rutile supported one and pure ceria. Turnover frequencies calculated from ammoxidation rates and irreversible O-2 uptakes in respect to a particular picoline isomer were almost equal for pure supports on one hand and for supported ceria catalysts on the other. The two structural isomers, beta- and gamma-picolines seem to have exhibited marked steric effect in their reactivity in catalysis on the catalysts.