The zygomaticofrontal suture is a strong joint needed for protection of the orbit. During infancy its development can be altered by local mechanical factors which prevent its complete union. The following case report of a man with a slowly growing lesion of the left orbit was found to have a large dermoid cyst communicating with the temporal fossa. Presumably, the presence of choristomatous tissue at the junction of the zygomatic and frontal bones prevented normal closure of the joint during infancy. The computed tomographic findings in this condition are pathognomonic of dermoid cyst.