[ Objective ]The aim of this study was to investigate the relationship between the Methylenetetrahydrofolate reductase (MTHFR) C677T, excision repair cross-complementing group 1 (ERCC1) genetic polymorphisms and the clinical efficacy of gemcitabine-based chemotherapy in advanced non-small cell lung cancer (NSCLC). [Methods]Included in the study were 135 patients diagnosed with unresectable advanced NSCLC treated with gemcitabine-platinum -regimens. The polymorphisms of MTHFR C677T, ERCC1 C8092A and ERCC1 C118T were genotyped using the TaqMan methods. Results were analysed by Cox model for survival and by logistic regression for response. [ Results ]The overall response rate was 28.9％.The response rate of patients with MTHFR CC genotype was higher than that of patients with variant genotype (TT or CT) (41.2% vs. 19.1%, P= 0.013). Median time to progression of patients with MTHFR CC genotype was longer than that of patients with variant genotype (7.6 months vs. 5.0 months, P= 0.003). No significant associations were found among ERCC1 C118T and C8092A polymorphisms and both response and clinical outcome. [ Conclusions ] Our data suggest the role of MTHFR C677T polymorphism as a possible predictive marker of response and TTP in advanced NSCLC patients treated with gemcitabine/ platinum.