Pure and Ln 3+ modified TiO 2 photocatalysts (Ln 3+ = Eu 3+ or Sm 3+ ions) synthesized by a sol–gel method as well as commercially available P25 were applied for photocatalytic generation of useful hydrocarbons and hydrogen from acetic acid. Structure and surface properties of the photocatalysts were characterized by XRD, UV–vis/DR, FT-IR and N 2 adsorption–desorption measurements. The main gaseous products of CH 3 COOH decomposition were CH 4 and CO 2 . Trace amounts of C 2 H 6 and H 2 were also detected in the reaction mixture. Moreover, it was observed that the quantities of all identified gases increased with elongation of irradiation time. The most active photocatalysts towards CH 4 and H 2 generation were Ln 3+ /TiO 2 containing 0.05 mol % of Sm and Eu, respectively. The results revealed that the Ln 3+ modification can improve the effectiveness of the photocatalysts compared to pure and commercially available TiO 2 provided that a proper amount of modifying ions is used.