To better understand the evolvement of the pulmonary dysfunction in the aging ventricular septal defect (VSD) patient, we invited adult patients with a congenital VSD and healthy age- and gender-matched controls for static and dynamic spirometry, impulse oscillometry, multiple breath washout, and diffusion capacity for carbon monoxide testing. Primary outcome was forced expiratory volume in 1 second. In total, 30 patients with a surgically corrected VSD (mean age 51 ± 8 years), 30 patients with a small, unrepaired VSD (mean age 55 ± 1 years), and 2 groups of 30 age- and gender-matched, healthy controls (mean age 52 ± 9 years and 55 ± 10 years, respectively) were included. Median age of radical surgery was 6.3 (total range: 1.4 to 54) years and median follow-up after surgery was 40 years (total range: 3.4 to 54). Compared with healthy matched controls, surgically corrected VSD patients had lower forced expiratory volume in 1 second, 87 ± 19% versus 105 ± 14% of predicted, p <0.01, lower forced vital capacity, 92 ± 16% versus 107 ± 13% of predicted, p <0.01, and lower peak expiratory flow, 100 ± 21% versus 122 ± 16% of predicted, p <0.01. Furthermore, corrected VSD patients revealed increased airway resistance in the small airways, 30 ± 22% versus 15 ± 14% of total resistance, p <0.01, and reduced diffusion capacity, 84 ± 12% versus 101 ± 11%, p <0.01. Patients with a small, unrepaired VSD had comparable pulmonary function to their matched controls. In conclusion, VSD patients 40 years of age or older demonstrated significant impaired pulmonary function in terms of reduced dynamic pulmonary function, increased airway resistance in the small airways, and reduced diffusion capacity up to 54 years after defect closure compared with healthy age- and gender-matched controls.