In a series of 410 coronal CT scans performed to assess paranasal sinus disease, we have identified eight cases in which an ethmomaxillary sinus was present. The ethmomaxillary sinus was unilateral in five cases and bilaterally present in three. The sex incidence was equal. Four patients had generalized mucosal disease of their paranasal sinuses which included the ethmomaxillary sinus whereas four patients had osteomeatal complex disease and sparing of their ethmomaxillary sinus. The characteristic radiological features of an ethmomaxillary sinus were drainage into an enlarged superior meatus, reduction in the size of the maxillary sinus and a normal bony orbital cavity. The differential diagnosis of an apparently hypoplastic maxillary sinus is briefly discussed.