PURPOSE: To evaluate the frequency, location, and signal intensities of parenchymal (cortical andsubcortical) tubers and white matter lesion, as seen on MR images of patients with tuberous sclerosis. MATERIAL AND METHODS: Twenty patients diagnosed on the basis of clinical and MR findings as suffering from tuberoussclerosis, were retrospectively reviewed. Their ages ranged from 6 days to 21 years (mean, 5.2 years), and theywere divided into two groups according to age : under 18 months (n=9) and over 18 months(n=11). We analyzed thefrequency, location, and enhancement patterns of tubers and white matter lesions, and the difference of signalintensities between cortical and subcortical tubers according to age. RESULTS: Cortical tubers were detected in11 patients (55%), subcortical tubers in 18 (90%), and white matter lesions in 16 (80%). Subcortical tubers weremore frequently noted than cortical tubers and the two types did not always accompany each other. Cortical tuberswere most commonly located in the frontal lobe(10/11), followed by the parietal lobe(2/11), and temporallobe(2/11). Subcortical tubers were also most commonly located in the frontal lobe(17/18), followed by thetemporal lobe(10/18). White matter lesions were also frequently observed in the frontal lobe(13/16) and wererelated to the location of parenchymal tubers in 12 of 16 white-mater lesions. There were no lesions in thecerebellum. The signal intensities of cortical and subcortical tubers were different in all patients. Those ofsubcortical tubers showed no significant difference between the two age groups, but in patients under 18 months,signal intensity on T1WI tended to be high(5/6), and on T2WI, tended to be low(5/6). In 15 patients, Gd-DTPAenhanced MR images showed no demonstrable enhancement, except in one case involving white-matter lesion. CONCLUSION: Both cortical and subcortical tubers were commonly located in the frontal lobe, but the latter weremore frequently observed than the former. Subcortical tubers did not always accompany cortical tubers, and on MRimaging, the signal intensities of the two types were different in all cases. Differentiation of cortical andsubcortical tubers by MR imaging may therefore help analyze the parenchymal tubers seen in tuberous sclerosis.