Purpose To determine the midterm outcome of lateral thoracotomy (LT) in skeletally immature patients concerning thoracogenic scoliosis development and lung parenchyma resection (LPR) extent. Methods In total, 129 children met the inclusion criteria: (1) LT during the study period; (2) skeletally immature at the time of LT; (3) clinical and radiographic follow-up of at least 3 years; and (4) no spinal or thoracic deformity on radiographs before LT. Patients were grouped according to their underlying disease, age at LT, and LPR extent. Radiographic parameters were assessed. Kaplan–Meier survival curves and univariate and multivariate analysis were performed. Results Of 129, 108 patients underwent pneumonectomy (9; 9.1%), lobectomy (79; 61.2%), segmentectomy (20; 15.5%) and 21 patients LT without LPR. The mean age at LT and at last radiological follow-up was 5.5 years (birth-17.8) and 15.2 years (3.4–33.2). The mean follow-up was 10 years (3–28.1). Scoliosis developed on average 5.3 years after LT. The mean Cobb angle was 22.1° (11–90°); > 10° in 37/129 patients (28.7%), of whom 5/129 (3.9%) had > 45°. The average vertebral rotation was 16.2° (2–43°; grade 0–II). RVAD was 26.5° (8°-33°) and 15.3° (2–43°) in patients with Cobb > 45° and ≤ 45°. Gender, age at surgery, and extent of LPR were not risk factors for post-thoracotomy scoliosis (p > 0.05), although younger patients developed a more severe deformity. Conclusion Although post-thoracotomy scoliosis is not associated with significant rotation, the risk of curve progression > 45° is relatively high. Regular follow-up is required as scoliosis may develop several years after LT with or without LPR.