PURPOSE: To evaluate whether there are any differences in MR findings between the childhood and the adult moyamoya disease. MATERIALS AND METHODS: We compared the brain MR findings in 22 children (13 boys and 9 girls, 2–18 years of age) who had moyamoya disease with 15 adult patients (7 men and 8 women, 19-55 years of age). The MR findings were classified as parenchymal-(infarctions and intracranial hemorrhages) and vascular abnormalities (intracranial vascular patency and moyamoya vessels). The difference in each of these MR findings was analyzed using Chi-squaretest and Fisher's exact test (two-tailed). Out of 22 children, two children with normal MR finding were excluded from the statistical analysis. Moyamoya diseases were diagnosed angiographically in all adult patients. In children, they were diagnosed by MR imaging, MR angiography(6), and/or conventional cerebral angiography(18). RESULTS: In children, cerebral infarctions were observed in 20 of 22 patients (91%) (cortex 86%, periventricular white matter/centrum semiovale 32%, basal ganglia 10%). In two patients, there was no parenchymal abnormality. Intra-cranial hemorrhages were not demonstrated in any patients. In adults, intra-cranial hemorrhages(intracerebral hematoma, intraventricular hemorrhage, alone or combined) were demonstrated in 10 of 15 patients(67%). Cerebral infarctions with or without intracranial hemorrhage were detected in 10 of 15 patients(67%)(cortex 40%, periventricular white matter/centrum semiovale 53%, basal ganglia 20%). The difference in parenchymal abnormalities between the childhood and the adult moyamoya disease was statistically significant (p=0. 000164). There was no significant difference between the two groups with regard to the occlusive changes of the internal carotid and middle cerebral arteries or to moyamoya vessels(p>0.01 ). CONCLUSION: This study could prove the fact that the principal clinical symptoms in the childhood moyamoya disease were due to cerebral infarction and those in the adult cases were due to infarction and intracranial hemorrhage. In addition, cortical infarction was more prevalent in children and infarction in periventricular white matter/centrum semivoale and basal ganglia was more frequentin adults. There was no significant difference in vascular abnormalities between the two groups.