Introduction: Objective evaluation of nasal function is a constant challenge for plastic surgeons, otolaryngologists, and allergists. The modified Glatzel mirror can evaluate nasal expiratory flow; however, there is little information on this method and its use in the measurement of nasal patency after surgical procedures. Objective: To compare, in a prospective study, the functional results before and after cosmetic rhinoplasty and evaluate the use of the Glatzel mirror as an objective method to assess nasal patency. Methods: To achieve this objective, we analyzed the functional results of surgery through a subjective questionnaire and objective evaluation through a modified Glatzel mirror, and evaluated the correlation between the 2 methods. Twenty patients (14 women and 6 men) underwent aesthetic rhinoplasty using spreader grafts. Pre- and postoperative evaluation (90-120 days) included a respiratory quality score (subjective) and modified Glatzel mirror test (objective). Subsequently, the Spearman test was used to compare the pre- and postoperative subjective and objective data. Results: The subjective evaluation demonstrated a statistical difference between pre- and postoperative scores (8 ± 2 and 9.4 ± 0.7, P< 0.001). There was no statistical difference in mean nasal patency by modified Glatzel mirror. No statistically significant correlation was observed when comparing the modified Glatzel mirror values with the subjective scores reported by patients pre- or postoperatively. Conclusion: The Glatzel method lacks sensitivity in detecting patient-reported improvements in breathing following rhinoplasty. This suggests that the method is a poor assessment tool to detect small, post-surgical changes in the nasal airways.