Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder caused by recurrent upper airway collapse during sleep. Accurate identification of the site and pattern of upper airway obstruction is essential for selecting the appropriate treatment. Müller's maneuver has been widely used as an office-based assessment tool; however, it has limitations in reproducing natural sleep conditions. Drug-Induced Sleep Endoscopy (DISE) allows dynamic visualization of the upper airway under sedated conditions and may provide more accurate information about the level and pattern of airway collapse. This study aims to compare the findings of DISE with Müller's maneuver in patients with obstructive sleep apnea and to evaluate the diagnostic value of both techniques in upper airway assessment.