Objectives: Using both sleep physiological parameters and image data to evaluate the efficacy of extended uvulopalatal flap (EUPF) surgery in the treatment of obstructive sleep apnea (OSA). Material and methods: Fifty patients with OSA underwent EUPF that consisted of bilateral tonsillectomy, dissection and removal of the submucosal adipose tissue of the soft palate and supratonsillar areas, and imbrications and repositioning of the denuded uvulopalatal flap. Polysomnography (PSG) and 3-dimensional computed tomography (3-D CT) data were obtained at baseline and 6 months postoperatively. Good response to surgery was defined as a reduction of the respiratory disturbance index (RDI) to less than 20 events/h and a greater than 50% reduction of the baseline RDI. Results: Forty-two patients (84%) achieved good results. The RDI and minimal 02 saturation improved significantly (P <.0001) after EUPF. The postoperative 3-D CT evaluation showed a significant increase in the retropalatal space (P < .0001). The preoperative lateral diameter of retropalatal space was predictive of the change of RDI (R-2 =, 0.15, P = .05). The effect of increased retropalatal space (r = 0.59, P = .0415) was significant in patients with baseline RDI ranged from 31 to 60 events/h. Conclusions: With special emphasis on the removal of palatal fat, EUPF appeared to be effective in the reduction of sleep apnea in selected patients. 3-D CT proved that this technique was effective in widening the upper airway by relieving the retropalatal obstruction. (C) 2005 Elsevier Inc. All rights reserved.