To evaluate changes in pulmonary functions in patients with Type 2 diabetes mellitus (DM), 25 diabetics [mean age 55.6±9.9 years (33-68 years), mean duration of diabetes 9.4±7.5 years (0-30 years), 20 women and 5 men] were studied. The control group consisted of 10 healthy people mean age 46.8±10.4 years (33-65 years), (6 female, 4 male). Pulmonary function tests (PFT), arterial blood gas analysis (ABGA) were performed. Alveolary-capillary membrane permeability and regional distribution of ventilation were assessed with Tc-99m DTPA aerosol inhalation scintigraphy and perfusion scintigraphy was administered with Tc-99m MAA. PFTs and ABGA were found to be normal in diabetics. Patients with microangiopathy had higher HbA 1c and PaCO2 levels than those of patients without (p<0.05). Maximal inspiratory pressure was reduced in patients with microangiopathy (p<0.05). The patients who had HbA 1c levels >8% with poor glycemic control had higher PaCO2 levels (p<0.05) and showed a mild reduction in diffusing capacity for carbon monoxide (DLCO) and DLCO % (p<0.05). Pulmonary epithelial permeability assessed with Tc-99m DTPA aerosol scintigraphy did not show a significant difference in patients with DM and the control group. The clearance rates of the 2 upper lobes were slower in diabetics and in the group with complications. Also the total lung clearance and the clearance of both lungs were longer in patients with complications, which was not statisticaly significant. Inhalation and perfusion scintigrams showed small, subsegmental or nonsegmental perfusion defects mostly in the lower lung lobes in five patients with diabetic microangiopathy. In conclusion, mild changes were observed in pulmonary functions and inhalation perfusion scintigraphy considering the duration of DM, degree of metabolic control and pulmonary microangiopathy.