Backround: Surgical operations are alternative treatments in persons with Obstructive Sleep Apnea Syndrome who cannot tolerate continuous positive airway pressure therapy. Drug-Induced Sleep Endoscopy is a method with which somnolence is pharmacologically induced and collapse is evaluated through nasal endoscopy in patients with Obstructive Sleep Apnea Syndrome. Aims: We aimed to evaluate efficiency of dexmedetomidine or propofol used for sedation in patients undergoing drug-induced sleep endoscopy. Methods: A total of 40 patients aged between 18 and 65 years old in the ASA STATUS I-II group were included in the study. After premedication with midazolam 0.05 mg/kg intravenously, patients were randomly divided into two groups and administered intravenous (iv) propofol with the loading dose of 0.7 mg/kg for 10 minutes, followed 0.5 mg/kg/h infusion (Group P); or dexmedetomidine with the loading dose of 1 mcg/kg for 10 minutes, followed by 0.3 mcg/kg/h infusion (Group D). Haemodynamic and respiratuary parameters, Bispectral index score, Ramsey sedation score, time to achieve sufficient sedation, surgeon's and patients' satisfaction, postoperative Aldrete score and side effects were recorded. Results: Time to achieve sufficient sedation, Bispectral index scores at 5, 10 and 15th. minutes intraoperatively, first Aldrete score in the recovery room, SpO(2) values and respiratory rates all over the surgical procedure and in the recovery room were found lower in Group P (P<0.05). Bispectral index scores, mean arterial pressure and heart rate in the recovery room were significantly lower in Group D (P<0.05). Conclusion: Dexmedetomidine may be preferred as a safer agent with respecting to respiratory function compared with propofol in obstructive sleep apnea patients who known to be susceptible to hypoxia and hypercarbia.