ObjectiveThis observational cohort study aimed to evaluate ventilatory function (VF) and functional exercise capacity (FEC) in mild adolescent idiopathic scoliosis (AIS).MethodsSeventy-three adolescents with idiopathic scoliosis, aged approximately 10 to 17 years (mean age: 13.43 ± 1.27 years), with a Cobb angle less than 20° (mean: 16.44° ± 1.59°), met the inclusion criteria and were assigned to group A. Another 34 healthy adolescents with normal VF and FEC served as controls (group B). Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), maximum voluntary ventilation (MVV), and FEC (by the 6-minute walk test [6MWT]) were the main outcome measures.ResultsPost-study mean values of FVC, FEV1, FEV1/FVC, MVV, and the 6MWT were 2.42 ± 0.36 L and 3.26 ± 0.59 L, 2.14 ± 0.31 L and 3.03 ± 0.43 L, 88.13% ± 3.89% and 91.14% ± 4.67%, 76.96 ± 6.85 L/m and 107.61 ± 11.44 L/m, and 581.12 ± 12.25 m and 627.74 ± 15.27 m in groups A and B, respectively. Between-group comparisons showed significant differences in FVC, FEV1, FEV1/FVC, MVV, and the 6MWT.ConclusionMild pulmonary and functional restrictions start early in mild AIS. This issue requires immediate intervention to prevent further deterioration.