The preoperative diagnosis of intracranial arachnoid cysts has been simplified and made more rapid and accurate with computed tomography(CT) Using CT cisternography detailed anatomic and physiologic infor-mations of arachnoid cysts could be obtained. CT features of pathologically proven 21 arachnoid cysts that were examined at Chonnam National Universi-ty Hospital from June 1983 to May 1987 were analyzed. The results were as follows : 1.prevalent age group was the 1st decade (8 cases) and male to female ratio was 17:4. 2.Clinical features were related to the location of arachnoid cyst common symptoms were headache(53.3%) convulsion mental change and walking disturbance. 3.Locations of the arachnoid cyst were in supratentoral region (15 cases) most in middle cranial fossa (12 cases) and infratentoral region (6 cases) common at the retrocerebellar cisternal space (3cases). 4. Shapes of arachnoid cyst were biconvex with straight inner margin (8 cases) spherical (7 cases) simple biconvex (3 cases) and others (3 cases). 5. Size of thearachnoid cyst in the greatest dimension was ranged from 2 cm to 9 cm and commonly distributed between 3 cm to 5 cm (14 cases). 6. Of all 14 cases who did CT cisternography using metrizamide (11 cases) and iopamidol(3 cases) 2 cases had communication with the subarachnoid space.