To determine the influence of anatomical changes after orbital decompression to nasal function. We examined postoperative nasal function after orbital decompression in patients with GO in a prospective study. 25 patients were enrolled between 2014 and 2016. Sense of smell (Sniffin' Test) and nasal airflow (anterior rhinomanometry) were tested pre- and 6weeks postoperatively. In addition, postoperative incidence of sinus infections, persistent pressure pain, and infraorbital hypoesthesia were assessed by means of a questionnaire. The olfactory performance showed a significant increase (p < 0.05) after surgery, while the nasal airflow significantly decreased (p < 0.05). Acute sinus infection occurred in three, infraorbital sensibility disorders in eight cases within the first 6weeks after surgery. No persistent pain was recorded. We demonstrate that decompression of the medial orbital wall leads to a decrease in nasal airflow, whereof patients should be informed before the procedure. This is most likely due to a medialization of the medial turbinate and the prolapse of orbital content into the nasal cavity. The increase of the olfactory performance is, in our opinion, more likely due to variation within the standard deviation than to anatomical changes.