['Oxidative stress contributes to the development of both lung cancer and chronic obstructive pulmonary disease (COPD). Antioxidative enzymes may protect against such damage. We hypothesized that genetic variations in glutathione S-transferase M1 and/or T1 genes (GSTM1 and GSTT1, respectively) may influence susceptibility to COPD in patients with non-small-cell lung cancer.', 'The polymorphisms in GSTM1 and GSTT1 genes were examined in 110 patients (age: 63+/-1 years) with newly diagnosed non-small-cell lung cancer using the polymerase chain reaction. Respiratory function was assessed by bodyplethysmography.', 'In the GSTM1 null (-/-) genotype, both FEV1 and FEV1/FVC were significantly lower than in the GSTM1 plus genotype (GSTM1 -/+ or +/+) (75.8+/-2.5 versus 86.6+/-3.6%, p<0.02; 69.1+/-1.6 versus 77.0+/-2.4, p<0.01, respectively). Among the patients with GSTM1 null genotype, 49% suffered from COPD as opposed to 21% of patients with GSTM1 plus genotype. In contrast, no differences were seen in FEV1 or FEV1/FVC when comparing patients with GSTT1 null genotype and GSTT1 plus genotype (81.4+/-4.9 versus 79.3+/-2.3, p=NS; 71.1+/-2.9 versus 72.2+/-1.6, p=NS). Multiple stepwise regression analysis identified the GSTM1 genotype (p<0.02) as a significant independent predictor of FEV1 in this group of patients.'] Is glutathione S-transferase M1 gene polymorphism related to COPD in patients with non-small-cell lung cancer?