We assessed the presence of lung dysfunction in children with type 1 diabetes, evaluated as reduced diffusing capacity of the lung for carbon monoxide (DLCO), and its components: membrane diffusing capacity (DM) and pulmonary capillary blood volume (Vc). A total of 42 children, aged 15.6 ± 3.8 years, with type 1 diabetes for 8.3 ± 5.5 years, and 30 healthy age and sex-matched peers were recruited for the study. Lung volumes and spirometric dynamic parameters were assessed by plethysmography. Single-breath DLCO was measured according to international recommendation. DM and Vc volume were calculated. Lung volumes were significantly reduced in young patients with type 1 diabetes when compared to controls. Moreover, DLCO was reduced in patients compared to controls (78% ± 16% vs. 120% ± 1%, P = 0.0001). However, when differentiating DM and Vc compartments, we observed a significant impairment only about Vc (34 ± 20 ml vs. 88 ± 18 ml; P = 0.0001), while no difference was observed about DM compartment (23 ± 4 vs. 26 ± 3 ml/min/mmHg, P = 0.798). Whether this might be seen as the "first" sign of microangiopathic involvement in patients with type 1 diabetes has to be confirmed on larger groups but is still fascinating. Meanwhile, we suggest to screen DLCO in all patients with type 1 diabetes.