OBJECTIVE To explore the relationship between the extent of enlarged oropharynx and efficiency through measuring the anterior-posterior and transverse diameter of oropharynx of patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) before and after uvulopalatopharyngoplasty (UPPP). METHODS Thirty eight patients with OSAHS were studied. The following indexes were measured before and after UPPP: width of uvula base, length of uvula, distance between uvula and posterior pharyngeal wall (DBUP), distance between anterior pillar (DBPP), apnea-hypopnea index (AHI), body mass index (BMI) and SaO2. RESULTS The preoperative DBAP and DBPP were significantly less than those of normal adults (P < 0.05). DBUP, length of uvula and width of uvula base has no significant difference between preoperative patients and normal adults (P > 0.05). There was no significance difference in DBAP. DBPP and DBUP between postoperative patients and normal adults (P > 0.05). The preoperative AHI, IBM, minimal SaO2, mean SaO2, DBUP, DBPP, DBAP, length of uvula and width of uvula base has no significant difference between good responders and nonresponders (P > 0.1). CONCLUSIONS Transverse diameter of OSAHS patients is shorter than that of normal adults but anterior-posterior diameter of OSAHS patients has no difference compared with normal adults. Transverse diameter could be enlarged by UPPP. Not only anatomical abnormality but also other factors will contribute to the effect of UPPP.