A case of acromegaly associated to a giant osteoma of the cranial vault and hydrocephalus in a young woman is reported. It can be suggested that acromegaly favoured the marked growth of the osteoma. Hydrocephalus resulted consequent to both the compression of the superior longitudinal sinus by the tumor and alteration of the CSF resorption. The rarity of giant osteomas of the cranial vault associated with intracranial hypertension is pointed out.