ObjectiveTo explore the feasibility of applying circulating tumor cells (CTCs) and peripheral blood instead of tumor tissues for detecting XRCC1 Arg399 polymorphism.MethodsA total of 21 untreated patients with Non-small cell lung carcinoma (NSCLC) were recruited, and their tumor tissues，peripheral blood, and CTCs were analyzed for XRCC1 Arg399 polymorphism.Results from the 3 different sources (tumor tissues, peripheral blood, and CTCs) were compared against one another.ResultsThe results revealed that the patient number of CC genotype of XRCC1 Arg399 polymorphism in tumor tissues，peripheral blood and CTCs was 12, 11, 11; CT genotype 7, 9, 8; and TT genotype 2, 1, 2.There was no significant difference among three approaches to detect XRCC1 Arg399 polymorphism.(χ2=0.950，P=0.978).An agreement between tumor tissues and peripheral blood was found (16/21, 76.2%) and a significant correlation between tumor tissues and CTCs was observed (20/21, 95.3%).The concordance between CTCs and tumor tissues was much higher than it was between tumor tissues and peripheral blood.ConclusionCTCs and peripheral blood may potentially be a substitute for tumor tissues to identity XRCC1 gene polymorphism, and CTCs appear to have higher accuracy.