To assess postoperative changes of the upper airway in a pediatric syndromic cranial-synostosis (SCS) population who underwent Le Fort III (LFIII) or frontofacial advancement by distraction osteogenesis (DO). Charts' review of 25 SCS infants presented at our tertiary-care children's hospital between January 2005 and December 2016 was performed. Preoperative (T0) and postoperative (T1) three-dimensional computed tomography (3D-CT) and polysomnography (PSG) were recorded. Differences between T0 and T1 airway volumes and changes in PSG data were analyzed. 18 patients were included. The mean T0 and T1 volumes were calculated as 15.963 mm3 ± 7.181 SD and 24.550 mm3 ± 12.946 SD, respectively. Airway areas increased significantly (p < 0.05) in the total study-group by a median value of 8.004 mm3, together with a global 72.22% improvement in respiratory parameters. A statistically significant gain of the upper airway after LF III and DO in SCS patients has been demonstrated. Given the absence of a direct relationship between post-operative upper airway volume increase and OSAS degree improvement, further insights should consider performing T0 and T1 sleep endoscopy analysis to complete the diagnostic workup and to better assess the level of residual or recurrent upper airway obstruction in patients who experience unsuccessful surgical treatment.