Objective: Vanadium and vanadium compounds are responsible for insulin-like activity and can mimic the action of insulin through alternative signaling pathways. As the lung is a possible target organ for diabetic complications, the aim of the present study was to investigate the effect of vanadyl sulfate supplementation on the antioxidant system in the lung tissue of diabetic rats. Methods: Diabetes was induced by intraperitoneal injection of streptozotocin (STZ, 65 mg/kg body weight) to male Swiss albino rats. The rats were randomly divided into 4 groups: control; vanadyl sulfate control; STZ-diabetic untreated; STZ-diabetic treated with vanadyl sulfate. Vanadyl sulfate (100 mg/kg body weight) was given daily by gavage for 60 days. At the last day of the experiment, rats which were fasted overnight were sacrificed. Then, lung tissues were taken and homogenized in cold saline to make a 10% (w/v) homogenate. Antioxidant enzymes, catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, as well as carbonic anhydrase, myeloperoxidase and lactate dehydrogenase activities were determined in the lung tissue. Results: It was shown that vanadium supplementation decreased all enzyme activities tested which increased in the lung tissue of untreated diabetic group. Conclusion: Vanadium could be used as a preventive for diabetic complication because of its antioxidant activity.