Non–traumatic cerebrospinal fluid rhinorrhea is uncommon. Review of the literature revealed that 45% of cases are high pressure leaks and 55% of cases are normal pressure leaks. Meningoencephaloceles are very rare occurrences in the latter category and we present the third reported case occurring in the frontal sinus. Radiographically this lesion appeared as a mucocele because of its expansile nature, however non–traumatic mucoceles have not been associated with cerebrospinal fluid rhinorrhea. The only non–osseous expansile lesion of the paranasal sinuses found to be associated with this complication is the meningioencephalocele.