Background: The phenomenon of recirculation involves the circulation of mucous secretion between the natural ostium and other openings and is observed mainly after surgery when the surgical opening is not connected. Methods: Seven patients with a mucous stream transporting into an accessory ostium, as found during endoscopic examination, were entered into study. The coronal computed tomogram findings of the mucous recirculation were analyzed at three levels: anterior, middle, and posterior portion of it. Results: The anterior portion was visualized at the level of the natural ostium in five patients. The middle portion inside the maxillary sinus was visible in six cases. The posterior portion was visualized at the level of the accessory ostium in five patients. Among the axial scans, mucous rings were visible in two patients. Conclusions: The primary mucous recirculation between the natural and accessory openings is shown as a ring structure in coronal computed tomogram scans.