Objective: Flexible optic laryngoscopy (FOL) allows us to visualize the obstructive sleep apnea (OSA)-related airway passages. However, objective data presenting evidence of OSA through this perspective are lacking. The aim of this study was to quantify the surface area of the retropalatal region in control subjects and OSA patients utilizing FOL images. This was a prospective, case-control study. The study was performed at the otolaryngology department of a university hospital.