Background & Objectives: Diabetes mellitus (DM) is a significant public health problem worldwide which is associated with hormonal, metabolic and micro vascular abnormalities. The angiopathic complications affect eyes, kidneys, nervous, cardiovascular and respiratory system, which are primarily due to biochemical alterations in connective tissue. Materials & Methods: In this study, we included 100 subjects, 50 Diabetic (25 Male and 25 Female) and 50 (25 Male and 25 Female) healthy individuals aged 30-55 years. The pulmonary function tests were performed by the computerized spirometer in the Clinical Physiology Lab, Department of Physiology, Dr. PSIMS & RF, Chinnavutapalli. Results: The results of our study showed a statistically significant reduction in FEF50%, FEF75% & FEV1 /FVC ratio in diabetic male subjects when compared with control male subjects (p< 0.0001) and diabetic female subjects showed a reduction in FEV1/FVC which is not statistically significant (p = 0.0004) but we observed a statistically significant reduction in FEF50% & FEF75% in diabetic female subjects when compared with control female subjects (p< 0.0001). On spirometry, Diabetic subjects showed a significant reduction in FEV1/ FVC ratio, FEF 50%, FEF 75% relative to non diabetic controls. Conclusion: We conclude from our study that diabetic subjects showed impairment in lung function. We found a decrease in FEV1/FVC ratio, FEF50% and FEF75% in diabetic subjects as compared to control subjects.