OBJECTIVES/HYPOTHESIS High anterior septal deviation (HASD) is an underreported anatomic variant that can affect the decision to perform septoplasty for access during sinus surgery and ease of postoperative debridement. This study aims to 1) describe an objective method of assessing HASD, and 2) explore its prevalence and implications for performing septoplasty. STUDY DESIGN Retrospective cross-sectional study. METHODS Computed tomography scans from 2014 to 2020 were retrospectively reviewed. Two independent observers measured the following with respect to midline: distance to septum (SDD), distance to lateral nasal wall (LNW), and septal deviation angle (SDA). RESULTS A total of 147 patients were included, with excellent interrater reliability across 99 patients (0.8-0.9). Mean measurements across all patients were SDD (2.77 mm ± 1.34), SDD/LNW (0.26 ± 0.12), and SDA (8.9° ± 4.0). Of 102 patients who underwent sinus surgery, 47 received septoplasty. Compared to the non-septoplasty cohort, the septoplasty cohort had a greater mean SDD (3.61 mm ± 1.48 vs. 2.27 mm ± 0.95; d = 1.10 [95% CI 0.67-1.51]), SDD/LNW (0.34 ± 0.13 vs. 0.21 ± 0.09; d = 1.18 [95% CI 0.76-1.60]), and SDA (11.1° ± 4.3 vs. 7.3° ± 3.4; d = 1.00 [95% CI 0.58-1.40]). Receiver operating characteristic cutoffs were SDD ≥2.43 mm, SDD/LNW ≥0.25, and SDA ≥7.6°, corresponding to a 49%-58% prevalence of HASD. CONCLUSION HASD is relatively common and the methods described herein can reliably assess its dimensions. Measurements of SDD, SDD/LNW, and SDA exceeding cutoffs determined by this study may represent clinically significant deflections prompting consideration of septoplasty. These methods may aid in preoperative planning. LEVEL OF EVIDENCE 4 Laryngoscope, 2021.