The aim of this study was to investigate the effects of surgical intervention for nasal pathologies on obstructive sleep apnea syndrome (OSAS) and continuous positive airway pressure (CPAP) titrations in patients with OSAS. The study was designed as a prospective case control study. Between December 2007 and June 2010, 31 patients (26 men and 5 women) who were diagnosed with OSAS with polysomnography and confirmed to have obstructive nasal pathology were enrolled in the study. The average age of the patients was 53 ± 9.6 (range 33-68 years) and the body mass index ranged from 22 to 40.6 kg/m(2) with an average of 30.3 ± 4.1. The patients were evaluated with Epworth Sleepiness Scale, OSAS Complaints Questionnaire, visual analog scale, and CPAP titration before and 3 months after nasal surgery. As three patients did not attend the control polysomnography, data analysis was performed on 28 patients. Although there was a significant improvement in the nasal passage and subjective complaints, namely, snoring frequency, apnea and daytime sleepiness, the difference between preoperative and postoperative AHI values was not statistically significant. Postoperative CPAP titration results indicated a decrease both in pressures and in AHI in comparison to preoperative values. These reductions were not statistically significant, although the decrease in CPAP pressures was close to significance (p = 0.062). Nasal pathologies should be treated in all patients with OSAS, particularly those undergoing CPAP treatment. However, patients should be counseled that favorable results might not be achieved after nasal surgery.