20 cases of supratentorial arachnoid cysts are reported. Their classification according to the clinical symptomatology allows to separate them in 3 categories: those presenting with intracranial hypertension and/or a focal neurological deficit (7 cases), those presenting with headache (4 cases) or epilepsy (4 cases), those which were found incidentally and where asymptomatic (5 cases). The neuropsychological examination showed that 5 cysts of the left sylvian fissure had some memory deficit in the verbal modality, but remarkably none was found to have signs of aphasia on detailed testing. Indications for surgical treatment are discussed considering the various clinical groups, the results of neuropsychological evaluation and the neuroradiological findings.