CONCLUSIONS Rhinosinusitis detected by preoperative osteomeatal unit computed tomography (OMU CT) may not increase the incidence of postoperative central nervous system (CNS) infections. OBJECTIVES To evaluate the safety of endoscopic endonasal transsphenoidal pituitary surgery in patients who had rhinosinusitis detected by preoperative OMU CT. METHODS A total of 107 patients who underwent endoscopic endonasal transsphenoidal pituitary surgery were enrolled. The presence of rhinosinusitis and the location of involved sinuses were assessed by preoperative OMU CT. The extent of pituitary tumors was assessed by preoperative sellar MRI. The occurrence of intraoperative cerebrospinal fluid (CSF) leakage and postoperative central nervous system (CNS) complications were analyzed using the medical records. The correlations between these variables and postoperative CNS complications were examined. RESULTS After pituitary surgery, postoperative CNS complications occurred in four patients (3.7%). Twenty-eight patients (26.2%) had findings of rhinosinusitis on preoperative OMU CT. Of the 28 patients, 8 had rhinosinusitis in the anterior sinuses and 20 in the posterior sinuses. Intraoperative CSF leakage occurred in eight patients (7.5%). The occurrence of intraoperative CSF leakage showed a significant correlation with the incidence of postoperative CNS complications (p = 0.003) but not with the presence of rhinosinusitis (p = 0.134). Although not statistically significant, patients with rhinosinusitis in the posterior ethmoidal and/or sphenoidal sinuses tended to have higher incidences of postoperative CNS complications (p = 0.057).