Fibrous dysplasia is a bone disease of unknown etiology in which cellular fibrous tissue gradually replaces normal bone and involves the cranium infrequently. Recently, we have experienced 3 cases of fibrous dysplasia which involved the frontal, sphenoid and parietal bones with vault deformity. The 2 cases, in which the frontal and sphenoid bones were involved, presented with proptosis and exophthalmos. All of the cases manifested vault deformity which caused cosmetic problems. We performed decompressive and plastic surgery for the purpose of relieving the compression of cranial nerves and for the sake of the cosmetic effect. The clinical courses were uneventful.