Background: The lung has not been considered routinely as a seat of target organ damage in patients with diabetes mellitus (DM) even though DM has proven detrimental effects on the microvasculature and connective tissue. We intended to compare the lung functions of patients with DM and healthy individuals. Methods: This was a single-center, observational, prospective, cross-sectional, case-control study done from July 2021 to June 2023. Spirometery parameters (including forced expiratory volume in first second (FEV1), Forced vital capacity (FVC), and FEV1/FVC ration) of non-smoker patients with Type 2 DM without lung diseases in the age-group of 20-60 years were compared with healthy, never-smoker, non-diabetic individuals.were enrolled as controls. Results: A total of 123 DM patients and 129 healthy controls were enrolled.Mean duration of DM andHBA1C in cases were 7.2850±2.43 years and 7.78±0.63% respectively. The mean FVC, FEV1 were lower in DM as compared to healthy controls [p<0.001]. Patients with DM had a significantly less proportion [p<0.001] with normal spirometery [77 (62.6%) vs 113 (87.6%)] and higher proportion [p<0.001]with restrictive patterns of spirometery [34(27.6%) vs 9 (7.0%)]. FVC and FEV1 values differed significantly in patients with DM duration less than 5 years, 5-10 years and greater than 10 years. FVC, FEV1 and FEV1/FVC values did not differ significantly between cases with HBA1C < 7% and > 7%. FEV1 [correlation coefficient = -0.88], FVC [correlation coefficient = -0.89] negatively correlated significantly with duration of diabetes but not with age, BMI and HBA1C levels. Conclusions: Patients with DM have more incidence of restrictive pattern on pulmonary function testing than normal healthy controls. The duration of DM negatively impacts the pulmonary function in these patients.