Background and Objectives: Obstructive sleep apnea (OSA) is a sleep-related breathing disorder, characterized by disrupted snoring and repetitive upper airway obstructions. Continuous positive airway pressure (CPAP) is considered the therapeutic mainstay for OSA patients. However, CPAP therapy has compliance limitations. An alternative treatment options is maxillomandibular advancement (MMA) surgical procedure. Genial tubercle advancement (GTA) is often performed concomitant with MMA for esthetic purposes. Cone-beam computed tomography (CBCT) provides the ability to visualize the upper airway and perform three-dimensional (3D) reconstructions. The purpose of this study is to evaluate the impact of MMA procedure with or without GTA on oropharyngeal airway space in OSA patients and the stability after completion of orthodontic treatment. Methods: A total of 25 patients (18 females and 7 males) with a mean age of 37.1 ± 17.3 years were included in the study. CBCT scans were taken before treatment (T1); after pre-surgical orthodontic treatment (T2); immediately after MMA procedure (T3); and at 10 months follow-up visit (T4). Thus, (T2-T1) represented changes due to orthodontic treatment only; (T3-T2) represented changes due to MMA procedure; and (T4-T3) represented changes due to follow-up after surgery. Each patient served as his/her own control. Fifteen of the individuals underwent MMA with GTA. All DICOM files were analyzed using Dolphin 3D Imaging software program to determine total airway volume (TAV), airway area (AA) and minimum axial area (MAA) at explicit regions along the posterior airway space. Dolphin 3D voxel-based superimposition was used to determine the amount of skeletal advancement with MMA and changes after surgery. Results: Significant increase in TAV, AA and MAA was found with MMA treatment (40.61%; 28.77%; and 56.40%, respectively, p<.05). Smaller but significant decrease in TAV, AA and MAA was found during the 10 months follow-up visit (20%; 9.7%; and 26.8%, respectively, p<.05). No significant differences were found in airway measurements with or without GTA procedure. No significant differences were found in any of the airway measurements with or without GTA procedure. The average forward movements of the maxilla, mandible and chin were 6.56 mm and 8.21 mm, 11.42 mm, respectively and less than 1mm relapse was found during the follow-up period. No correlation was found between the magnitudes of skeletal advancement and the change in oropharyngeal airway space (OPAS). Conclusions: Significant increase in OPAS can be expected with MMA surgery with or without GTA procedure in patients diagnosed with OSA. Significant forward movement of the maxilla, mandible and chin positions can be obtained with MMA procedure. A partial loss in OPAS was found during the 10 months follow-up period. The surgical movements were found to be stable with less than 1 mm of relapse during the follow-up period, which was not clinically significant. iii DEDICATIONS To my Father, Saud, even though you are not with us anymo...