Objective: The supraglottic airway device (SGAD), which is widely used in anesthesia practice, is a safe method. The timing of SGAD removal is still controversial. The aim of this study was to compare conventional and ultrasonographic methods in deciding the timing of removal in patients with SGAD placement under general anesthesia. Methods: One hundred patients who underwent surgery under general anesthesia in a university hospital and underwent SGAD placement were included in the study. During the awakening process, patients were divided into two groups: the conventional group and the USG group. In the USG group, diaphragm thickness was recorded preoperatively and intraoperatively before SGAD removal. In the ultrasonography (USG) group, the SGAD was removed in patients with a diaphragmatic thickness (Δtdi) ratio of 20% or more in the USG measurement of the diaphragm. In the conventional group, SGAD removal was decided after eye opening, obeying orders, spontaneous or commanded breathing that produced >4 mL kg-1 tidal volume. Patients in both groups were compared in terms of SpO2 values, SGAD removal time, hemodynamic changes and postoperative complications. Results: There was no statistically significant difference between the groups in terms of completion of the operation and duration of anesthesia. No statistically significant difference was observed between the SGAD removal times in both groups. Heart rate, mean arterial pressure, systolic arterial pressure, diastolic arterial pressure and peripheral oxygen saturation values were similar in preoperative, intraoperative and postoperative periods between the groups. There was no difference in complication status in the postoperative period. Conclusion: Conventional methods do not have sufficient objectivity in deciding the time of SGAD removal in patients with SGAD placement. Ultrasonographic evaluation of diaphragmatic thickening has not been shown to be superior to the conventional method of deciding the timing of SGAD removal. However, the use of USG has the advantage of collecting measurable and objective data independent of the anesthesia provider. The lack of significant difference between the two groups may be explained by the experience of the clinician making the decision with the conventional method, and ultrasonographic evaluation may provide additional information to inexperienced users. Further studies are needed in other surgical procedures, risk groups and age groups to determine whether the use of USG in extubation decision-making would be useful. [ABSTRACT FROM AUTHOR]