The presentation of an enlarged pneumatized bulla ethmoidalis (BE) that obstructs the ethmoid infundibulum has not been previously reported. We report such a case in a 23-year-old woman who presented with recurrent acute rhinosinusitis and chronic rhinosinusitis. The obstruction had been caused by inferior and anterior pneumatization of the BE. Surgery was successful in alleviating all symptoms, and the patient remained symptom-free at 10 months of follow-up. We describe the radiologic and endoscopic findings in this case, and we discuss the possible mechanisms by which BE is involved in the pathogenesis of recurrent acute and chronic rhinosinusitis.