Purpose:.Cholesterol granuloma is usually associated with chronic middle ear disease..Involvement of the ethmoid sinus by cholesterol granuloma is rare..We describe a case with cholesterol granuloma of the posterior ethmoid sinus causing optic nerve compression..No previous reports were found in our review of the literature. Case report:.A 48-year-old man had impaired visual acuity and a relative afferent pupillary defect in the right eye. Fundus fluorescein angiography showed a swollen optic nerve head and optic disc leakage. Automated perimetry revealed a severe peripheral visual field defect with tunnel vision. Computerized tomography demonstrated an expansile,.isodense mass in the right posterior ethmoid sinus, remodeling of the bony walls of the right sphenoid sinus, and lateral displacement of the optic nerve in the right orbit..Compressive optic neuropathy caused by posterior ethmoid sinus lesion was diagnosed..A transnasal endoscopic exploration of the right ethmoid sinuses demon-strated a soft expansile cystic lesion with a thick yellow cap sule that filled the inside of the posterior ethmoid sinus. Brownish fluid with shiny crystals was drained by fine needle aspiration. The capsule was removed completely, and the mu-cociliary clearance of the sinus was reestablished..The patho-logic pictures confirmed the diagnosis of cholesterol granulo-ma, which included typical cholesterol clefts surrounded by inflammatory cells with focal multi-nucleated giant cells. Visu-al function fully recovered without recurrent lesions after a three-year follow-up. Conclusion:.Compressive optic neuropathy can be rarely caused by cholesterol granuloma in the posterior ethmoid si-nus. The visual prognosis may be good after transnasal endo-scopic decompression in such patients.