Three cases of arachnoidal cysts in children are reported; one of them in the posterior fossa and the others located above the tentorium. In all of them chronic intracranial hypertension was present. However, there was no visible bulging of skull related to the cyst localization. In two cases the etiology of the cyst was probably inflammatory and congenital in one. Surgery was the treatment of choice; there was a good result in two cases and one patient deceased.