Background and Aim: Obstructive sleep apnea (OSA) syndrome is predisposed to the development of upper airway obstruction during sleep, and it poses considerable problem for anesthetic management. Difficult intubation (DI) is an important problem for management of anesthesia. In this clinical research, we aim to investigate the relationship between DI and prediction criteria of DI in cases with OSA. Materials and Methods: We studied 40 [OSA (Group O, n = 20) and non-OSA, (Group C, n = 20)] ASA I-II, adult patients scheduled tonsillectomy under general anesthesia. Same anesthetic protocol was used in two groups. Intubation difficulties were assessed by Mallampati grading, Wilson sum score, Laryngoscopic grading (Cormack and Lehane), a line joining the angle of the mouth and tragus of the ear with the horizontal, sternomental distance, and tyromental distance. Demographic properties, time-dependent hemodynamic variables, doses of reversal agent, anesthesia and operation times, and recovery parameters were recorded. Results: Significant difference was detected between groups in terms of BMI, Mallampati grading, Wilson weight scores, Laryngoscopic grading, sternomental distance, tyromental distance, doses of reversal agent, and recovery parameters. Conclusion: OSA patient's DI ratio is higher than that of non-OSA patients. BMI Mallampati grading, Wilson weight scores, Laryngoscopic grading, sternomental distance, and tyromental distance evaluation might be predictors for DI in patients with OSA.