The optical and scintillation characteristics of Gd2YAl2Ga3O12: Ce and Lu2YAl2Ga3O12: Ce single crystals are investigated. At 662 keV gamma-rays, light yield (LY) of 37,900 ph/MeV and energy resolution of 7.0% obtained for Gd2YAl2Ga3O12: Ce are superior to those of 18,900 ph/MeV and 11.5% obtained for Lu2YAl2Ga3O12: Ce. Scintillation decays are measured using the time-correlated single photon counting technique. A fast component decay time of 45 ns with relative intensity of 88% obtained for Lu2YAl2Ga3O12: Ce is superior to that of 50 ns (65%) for Gd2YAl2Ga3O12: Ce. The linear attenuation coefficient at 662 keV gamma-rays is also determined and discussed.