Polymorphism of DNA base excision repair (BER) genes affects DNA repair capacity and may alter sensitivity to platinum-based chemotherapy regimens. This study investigated polymorphisms of OGG1 Ser326Cys, APE1 Asp148Glu APE1-141T/G and XRCC1 Arg399Gln for association with clinical outcome in 235 advanced inoperable nonsmall-cell lung cancer (NSCLC) patients after treatment with platinum-based chemotherapy. The multivariate analysis showed that OGG1 326 GC was associated with poor PFS [hazard ratio (HR) 1.730, p = 0.005], while XRCC1 399 GA, or GA+AA, was associated with poor OS in short-term period (HR 1.718, p = 0.003; HR 1.691, p = 0.003, respectively). Patients with OGG1 326/XRCC1 399 variant alleles had a higher risk to die early in short-term period (HR 1.929, p < 0.001). Furthermore, patients with XRCC1 399 variant allele (GA+AA) had higher risk of hematologic toxicity (p = 0.009), whereas patients carrying the OGG1 326 variant (GG), or the APE1-141 GG variant, had reduced risk of gastrointestinal toxicity (p = 0.015 and p = 0.023, respectively). The data from the current study provide evidence that OGG1 Ser326Cys, XRCC1 Arg399Gln, APE1 Asp148Glu, and APE1-141T/G polymorphisms may be useful in predicting clinical outcomes in patients with advanced inoperable NSCLC that will undergo platinum-based chemotherapy.Non-small cell lung cancer (NSCLC) is the most frequent form of lung cancer and often presents in an advanced inoperable stage. Patients are treated with platinum-based chemotherapy, but drug sensitivity and outcome are highly variable. Here, the authors examined the link between clinical outcome of treated patients and polymorphisms in DNA repair genes (OGG1, XRCC1, and APE1). They identified specific polymorphisms that were predictive for clinical outcomes of platinum-based chemotherapy such as early death, aggravated hematological or reduced gastrointestinal toxicities. These data are promising but further studies are needed to determine the usefulness of these polymorphisms as biomarkers in the clinical care of NSCLC patients.