PURPOSE: To describe MR findings and differential points of supratentorial cystic intracranial lesions. MATERIALS AND METHODS: We retrospectively reviewed and analyzed the MR findings of 59 patients with supratentorial cystic intracranial lesions, and classified them as follows: tumor-associated cyst, infectious cyst, ex-vacuo type cyst, and congenital/developmental cyst. RESULTS: Among 59 patients, 47 tumor-associated cysts were seen in 17, 42 infectious cysts in 13, 17 ex-vacuo type cysts in 10, and 19 congenital/developmental cysts in 19. In 44 of 47 tumor-associated cysts, increased or inhomogeneous internal signal intensity was seen on T1-weighted image, 37 of 47 showed thick uneven walls ; 35 of 47 had enhancing solid components and there was variable perifocal edema and mass effect. Infectious cysts were multiple (11 of 13). In cases of brain abscess, increased internal signal intensity on T1-weighted image, low signal intensity of abscess wall on T2-weighted image, thick even enhancing wall, and marked perifocal edema(4 of 4) were seen in all four cases. Cysts in cysticercosis were variable in appearance depending on the stage, but were smaller than other cystic lesions. Ex vacuo type cysts were of uniform CSF signal intensity in all pulse sequences and there was no identifiable wall or enhancement associated with enlarged adjacent ventricle and encephalomalacia(17 of 17). Congenital/developmental cysts showed a single lesion(19 of 19), a signal intensity similar to CSF in all pulse sequences(15 of 19), no identifiable wall(16 of 19), no enhancement(17 of 19), and no perifocal edema(19 of 19). CONCLUSION: MR was used to categorize supratentorial cystic intracranial lesions into four groups on the basis of their number, size, internal homogeneity of signal intensity on T1-weighted image, enhancing pattern, perifocal edema and mass effect, thereby improving diagnostic specificity and patient management.