There was analyzed single nucleotide polymorphisms of DNA excision repair enzyme genes hOGG, XPD, XPG, XRCC1 in 98 Siberian Group of Chemical Enterprises cancer patients and 148 healthy donors. No association was observed between the analyzed polymorphisms and malignant tumors in both control and subgroup (under study) of persons exposed to occupational ionizing radiation. Heterozygosis for the genes hOGG and XPD was found to be a protective factor to malignant tumors in exposed persons: the odds ratio = 0.42 (95% CI 0.18-0.98; p = 0.044) for the 326Ser/Cys genotype of the hOGG gene and 0.48 (95% CI 0.23-0.99; p = = 0.047) the 751Lys/Gln genotype of the XPD gene. The data obtained show a possible modifying role of the hOGG and XPD gene polymorphisms for malignant tumors risk in exposed persons.