The intention of the study was to find out whether in spite of carrying out the required protection measures in using therapeutic and diagnostic machines there is an increased frequency of structural chromosome aberrations in medical staff professionally exposed to ionizing radiation. The other objective was to find out whether there are consequential differences in exposure to Gamma and X radiation. The classic genotoxic method of analyzing chromosome aberrations in peripheral blood lymphocytes was used. and 200 metaphases per examinee were analyzed. Twenty-five staff members of Oncology Department exposed to Gamma radiation were examined by that method, 22 of Radiology Department exposed to X radiation, as well as 20 unexposed medical employees. The results have shown that chromatid breaks (CB) differ significantly in the three examined groups (p<0.05). The difference is even more significant in acentric fragments (AC), (p<0.001). In both the highest values are in the group of Gamma radiation exposure. Translocational aberrations (DIC) and tetraradiuses (TET) occured in the group exposed to Gamma radiation, while in other two groups that was not the case. There was a considerable positive correlation between the years of exposure to ionizing radiation and occurrence of acentric fragments. Aberration analysis per cell showed the highest frequency of structural aberrations in examinees exposed to Gamma radiation. It seems that protection measures in Gamma radiation departments are not always satisfactory. Furthermore, continual monitoring of Radiology Department staff exposed to X radiation is necessary, as their aberration frequency is higher than the control, the unexposed group of examinees.