Introduction: Surgically assisted rapid maxillary expansion associates a surgical procedure with orthodontic treatment.. The nasal patency can be objectively assessed through rhinomanometry, a test which simultaneously measures the flow and nasal pressure. Objectives: The aim of this longitudinal and prospective study is to investigate the skeletal changes occurring in the width of the nasal cavity after surgically assisted rapid maxillary expansion and to check, using rhinomanometry, the evolution of nasal patency. Materials and methods: The sample comprised 15 skeletally mature patients referred for SARME. A Hyrax-type appliance was used. The evaluation took place in two stages: T0 - before surgery, posterior-anterior cephalometric radiograph and rhinomanometry was performed. T1 - six months after surgery, posterior-anterior cephalometric radiograph and rhinomanometry was performed. The study includes a control group of 10 patients. In this group only rhinomanometric tests were performed, at T0 (the beginning of the study) and at T1 (six months after the first examination). Results: In the study group, there was an increase in nasal cavity width between T0 and T1and a decrease in the total nasal resistance between (TNR) T0 and T1. Regarding the control group, there was no changes in TNR. Conclusions: SARME had an effect on nasal permeability reducing the resistance. The width of the nasal cavity increased after surgery. It may be advisable to wait for conducting this intervention prior to the decision of additional interventions to improve the breathing capacity of the patients. Schlagwörter: Surgically assisted rapid maxillary expansion, SARME, nasal patency, rhinomanometry