Mild COPD is an asymptomatic disease but as oxidant antioxidant imbalance increases the severity of the disease also increases. The aim of the present study was to evaluate the oxidant antioxidant imbalance in mild and moderate COPD groups. The present study included 73 patients with COPD out of which 32 were of Mild impairment and 41 were suffering from Moderate COPD. The results indicated that the mean BMI of Moderate COPD group was lower as compared to Mild COPD group. The lung functions namely FVC, FEV1, FEV1/FVC % and FEV1% Predicted were significantly reduced in Moderate COPD group. The serum levels of antioxidant enzymes were significantly lower in Moderate COPD group as compared to Mild COPD group SOD units/mgm of serum protein(9.19±0.09 Vs 8.95±0.08 P<0.01) ; Catalase units/mgm of serum protein(8.95±0.06 Vs 8.88±0.07 P<0.01) ; GPX nmol NADPH oxidized/min/mgm of serum proteins(54.32± 0.38 Vs 52.95± 0.32 P<0.01 respectively). The mean Pack Years in Moderate COPD group is more thus indicating smoking induced Oxidant Anti-Oxidant imbalance in disease severity as compared to Mild COPD group in which the Pack Years were less. In present study in COPD patients MDA correlated inversely with SOD (r=-0.744,p=0.01),Catalase(r=0.346,p=0.01),GPX(r=- 0.682,p=0.01),FEV1(r=-0.446,p=0.05) and FEV1% Predicted(r=-0.567,p=0.01) The present study indicates that severity of oxidative stress is associated with lung function decline and also decrease in the anti oxidant enzymes levels which in part also contribute to disease severity.