We reviewed the clinical prognosis and therapeutic aspects in the management of pediatric moyamoya disease from our data base for the last 8 years since establishment of our institution. We found 99 cerebrovascular disease cases among the total of 1,159 cases, and 20 out of them were moyamoya disease. Only 13 cases were analyzed as the rest were not available for follow up. Nine girls and 4 boys were admitted with an average age of 5 years-old 4 months. Initial symptom were TIA in 5, cerebral infarction in 5, migraine in 2, and epilepsy in one. The type of moyamoya disease was bilateral type in 10 cases, and unilateral type in 3 cases. Clinical condition and investigations, as well as the effect of conservative management, required surgery in 9 cases (8 indirect revascularization and one direct-bypass surgery), and the rest 4 cases were managed conservatively. Only 10 cases were followed-up, 9 operated cases and one conservatively managed case. In 6 of 9 of the operated cases, there was recurrence: cerebral infarction in 3, TIA recurrence in 2 and epileptic seizure in one. On MRA a steno-occlusive lesion of PCA was found in 4 of the 6 recurrence patients, and improvement was achieved by additional surgery in one of them. All of the cases developed good postoperative collateral circulation. The conservatively treated patient did not show neither steno-occlusive lesion of PCA, nor a clinical recurrence for 7 years observation. Therefore, posterior circulation system in moyamoya disease is important as a collateral circulation in addition to the revascularization procedures, and we believe that the progression of the steno-occlusive lesion of PCA is an important indicator, predicting recurrence.