Background: The frontal sinus is considered the most challenging sinus to address surgically. There are no current classifications of the degree of surgical complexity of different frontal sinus configurations. The aim of this study is to develop a classification system of the degree of complexity of frontal recess surgery based on preoperative computed tomography (CT) scans.Methods: Authors were asked to submit a classification system. These were circulated to all authors. Selection of the final 3 classifications was based on a majority consensus. These classifications were compared further for time-taken, ease-of-use, and interrater agreement. These were assessed by the authors on 10 CT scans representing a range of anticipated surgical difficulty.Results: Out of 3 compared classifications, classification A was the quickest to score (1.44 minutes vs 1.57 minutes and 2.25 minutes), subjectively easiest (3.23 vs 4.07 and 5 on a visual analogue scale [VAS]), and had a moderate interrater agreement (0.52 vs 0.42 and 0.79). In addition, the grading of complexity was as good whether measurements were taken on the CT scans or whether size of the frontal ostium was visually estimated.Conclusion: We propose a fast, easy classification to anticipate the complexity of surgery in the frontal sinus and recess, for patients undergoing primary surgery. (C) 2016 ARS-AAOA, LLC.