The results of investigations of the influence of gamma and proton radiations on absorption, luminescence and birefringence of either pure or Cu, Fe and Cr doped LiNbO₃ single crystals were presented. A method of birefringence dispersion testing on the entire areas of plane-parallel plates of LiNbO₃ crystals has been illustrated by the influence of both types of irradiation on pure and Fe, Cr and Cu-doped LiNbO₃ wafers. It was found that LiNbO₃ LN:Cu single crystal shows a different behavior compared with other investigated crystals. First of all it exhibits lower susceptibility to g–rays, the absence of 500 nm additional absorption, and a strong proton susceptibility observed in polarimeter measurements.