Treatment of dentofacial deformities with jaw osteotomies has an effect on airway anatomy. Mandibular setback surgery and bimaxillary surgery in treatment of class III patients, have reducing effect on the size of pharyngeal airway space (PAS). The purpose of this study was to evaluate effects of these two treatment plan on PAS individually and also in comparing to each other. Cephalometric radiographs of 44 class III patients (27 mandibular setback surgery cases and 17 bimaxillary surgery cases) before and 6 month postoperatively were analyzed. In this study, 20 linear and 3 angular parameters were evaluated. Baseline measurements(severity of malocclusions) were similar in both groups (p> 0.05). Results showed constricting effect of both treatment plan on PAS but there wasn’t any significant difference between them. This study showed that bimaxillary treatment plan is not a suitable alternative for mandibular setback surgery in reducing the risk of airway obstructive problems.