Light yield and light loss coefficient of Lu3Al5O12:Ce (LuAG:Ce) and Lu3Al5O12:Pr (LuAG: Pr) single crystals grown by the Czochralski method were investigated under excitation with alpha-and gamma-rays. Photoelectron yield and energy resolution were measured using the XP5200B photomultiplier. The dependence of photoelectron yield on sample height was measured under excitation with a-and.-rays and the light loss coefficient was evaluated. It was found that the light loss coefficient of LuAG: Ce is smaller than that of LuAG: Pr. The ratio of photoelectron yield under excitation with alpha-and gamma-rays (alpha/gamma ratio) was also determined and discussed.