Thornwald's cyst is a benign bursa formation of the posterior superior wall of the rhinopharynx due to occlusion of the pharyngeal bursa, this entity has been known for more than a century but it is only exceptionally observed. A series of 3 cases have been diagnosed at Hôpital Saint-Antoine over the last 6 months and the perfect visualization of the cysts by CT scan and MR imaging wall no doubt allow their fortuitous detection more frequently.