In this work, we present results of studies aimed at optimization of scintillation performance of fast but low-light yield YAlO3:Pr scintillator. We applied co-doping with trivalent ions Mo3+ and Ga3+ in attempts to reduce the concentration of charge trapping centers that may exist in this material. Systematic study was performed by using the micro-pulling-down method for single crystal growth. Square-shaped YAlO3:(Pr,MO) and YAlO3:(Pr,Ga) crystals with selected co-dopant concentrations were grown. Experimental results including absorption spectra, luminescence under X-ray excitation and scintillation decay are presented. No positive contribution of the co-dopant ions was found. Complicated co-dopant behavior makes the improvement of scintillation parameters difficult. (C) 2008 Elsevier B.V. All rights reserved.