Transparent Lu0.8Sc0.2BO3 crystals doped with 1 at%Ce3+ and co-doped with 1 at% and 3 at%Ga3+ were grown by the Czochralski method. We applied absorption spectrum, luminescence spectra under UV and X-ray excitation, fluorescence decay curve, three dimensional thermoluminescene and X-ray absorption near edge spectroscopy to study the effect of Ga3+ co-doping on the Lu0.8Sc0.2BO3:Ce scintillation crystals. Experimental results indicated that no positive contribution of the Ga3+ ion doping on the scintillation efficiency was found. The causes for the deterioration of scintillation efficiency by co-doping Ga3+ were revealed. The decrease of practical cerium content and the Ce3+/Ce4+ ratio in crystals, and the increase of the trap concentrations, although the corresponding trap types still maintained the same, played a joint influence on the degrading of scintillation efficiency of Lu0.8Sc0.2BO3:Ce crystals. (C) 2012 Elsevier B.V. All rights reserved.