The purpose of this study was to investigate, through cone beam computed tomography, volumetric changes to the upper airway space in patients with skeletal class III skeletal deformities who had undergone mandibular setback surgery (group A [n = 24]) or bimaxillary surgery (mandibular setback surgery and maxillary setback Le Fort I osteotomy; group B [n = 23]). All of the patients underwent a cone beam computed tomographic examination for assessment of the upper airway volume and skeletal changes before surgery (T0) and 6 months after surgery (T1). In an evaluation of the anatomic characteristics of the upper airway, the anteroposterior length (APL), the largest transverse width (LTW), and the cross-sectional area (CSA) on the axial planes (the posterior nasal spine-posterior point of vomer (PNS-Vp), 1st cervical vertebra (CV(1)), 2nd cervical vertebra (CV(2)), 3rd cervical vertebra (CV(3)), and 4th cervical vertebra (CV(4)) planes) were calculated at T0 and T1. No significant differences between the groups A and B (P > 0.05) were found. In group A, the mandibular setback movement affected the oropharyngeal and hypopharyngeal volumes and reduced the APL, the LTW, and the CSA on the CV1, CV(2), and CV(3) planes (P < 0.05). The APL and the CSA on the CV(4) plane also were reduced (P < 0.05). In group B, the maxillary and mandibular setback movement narrowed the upper airway volumes. Specifically, the APL on the CV(1), CV(2), CV(3), and CV(4) planes, the LTW on the PNS-Vp, CV(1), and CV(3) planes, and the CSA on the PNS-Vp, CV(1), CV(2), CV(3), and CV(4) planes decreased after the surgery (P < 0.05). Between the 2 groups, there were statistical differences (P < 0.05) in the APL, the LTW, and the CSA on the PNS-Vp plane.