The scintillation properties of Lu1.8Y0.2SiO5:Ce (LYSO:Ce) and LaCl3:Ce scintillators were studied under g-ray excitation. For 662 keV g-rays (137Cs source), energy resolution of 4.5% obtained for LaCl3:Ce coupled to XP5200B PMT is much better than that of 8.2% for LYSO:Ce. The estimated photofraction of 26.1% at 662 keV for LYSO:Ce is higher than that of 15.7 % for LaCl3:Ce. The non-proportionality of the light yield and energy resolution versus g-ray energy were measured and the intrinsic resolution of the crystals was calculated. The coincidence timing resolution, obtained in this work for 511 keV annihilation quanta, was 222 and 229 ps, respectively, for LYSO:Ce – and LaCl3:Ce – based detectors in coincidence with a BaF2 detector.