© 2019 by the American Diabetes Association. OBJECTIVE Type 2 diabetes exerts a deleterious effect on lung function. However, it is unknown whether an improvement in glycemic control ameliorates pulmonary function. RESEARCH DESIGN AND METHODS Prospective interventional study with 60 patients with type 2 diabetes and forced expiratory volume in 1 s (FEV1) £90% of predicted. Spirometric maneuvers were evaluated at baseline and after a 3-month period in which antidiabetic therapy was intensified. Those with an HbA 1c reduction of ‡0.5% were considered to be good responders (n = 35). RESULTS Good responders exhibited a significant improvement in spirometric values between baseline and the end of the study (forced vital capacity [FVC]: 78.5 6 12.6% vs. 83.3 6 14.7%, P = 0.029]; FEV1: 75.6 6 15.3% vs. 80.9 6 15.4%, P = 0.010; and peak expiratory flow [PEF]: 80.4 6 21.6% vs. 89.2 6 21.0%, P = 0.007). However, no changes were observed in the group of nonresponders when the same parameters were evaluated (P = 0.586, P = 0.987, and P = 0.413, respectively). Similarly, the initial percentage of patients with a nonobstructive ventilatory defect and with an abnormal FEV1 decreased significantly only among good responders. In addition, the absolute change in HbA 1c inversely correlated to increases in FEV1 (r = 20.370, P = 0.029) and PEF (r = 20.471, P = 0.004) in the responders group. Finally, stepwise multivariate regression analysis showed that the absolute change in HbA 1c independently predicted increased FEV1 (R 2 = 0.175) and PEF (R 2 = 0.323). In contrast, the known duration of type 2 diabetes, but not the amelioration of HbA 1c , was related to changes in forced expiratory flow between 25% and 75% of the FVC. CONCLUSIONS In type 2 diabetes, spirometric measurements reflecting central airway obstruction and explosive muscle strength exhibit significant amelioration after a short improvement in glycemic control.