Methods of two-and three-crystal X-ray high-resolution diffractometry were used to investigate structural changes in Сz-Si single crystals irradiated with high-energy electrons (Е=18 МeV). The results of experimental investigation were interpreted by means of a generalized dynamic theory of X-ray diffraction in real crystals with randomly distributed microdefects of various types and a damaged surface layer. As dominant defects, disc-shaped and spherical clusters -SiO 2 precipitates, as well as dislocation loops were used.