In the present study we noted the effects of different photoperiodic regimes, i.e. long (LP; 20L:4D), short (SP; 4L:20D) and natural day length under diabetic condition in albino rats. We checked the oxidative stress of lung tissue by noting down the variation in antioxidant enzymes (superoxide dismutase and catalase) levels and lipid peroxidation in terms of malondialdehyde level. SP increased the activity of antioxidant enzymes and decreased lipid peroxidation. LP decreased the activity of antioxidant enzymes and increased lipid peroxidation. These findings suggest that photoperiodicaly regulated melatonin might be acting as an antioxidant for the free radical load of lung tissue during diabetic condition.