A few reports for ERCC1 SNPs were conducted in patients treated with cisplatin chemotherapy. The aim of this study is to determine whether the SNPs are a prognostic factor related to the treatment or not and if smoking level of the patients have any relationship to the SNPs' effect on the survival. Peripheral blood lymphocytes of 423 consecutive non-small cell lung cancer patients were examined: 245 of the patients received cisplatin combination chemotherapy and 178 received only conservative care. We examined ERCC1 SNPs (codon 118 C/T and 8092 C/A). Whereas ERCC1 118 SNP had no effect on the survival in patients' given no treatment, an effect of the SNP was observed in the treatment group, especially in stage III. When smoking was considered, the risk effect of the T allele was shown to be significantly associated with the group that had more than 50 pack yr (p=0.03). As for the ERCC1 8092 C/A, no significant effects were observed in the treated group and the non-treatment group. These findings may suggest that the ERCC1 118 SNP is an useful prognostic factor related to cisplatin therapy and the effect of this polymorphism appears to be modified by smoking.