Moyamoya disease is a chronic progressive vascular disease of brain characterized by bilateral stenosis or occlusion of the arteries around the circle of Willis with prominent arterial collateral circulation. We introduce here a patient with Moyamoya who was misdiagnosed. She was a 16-yr-old female from north east of Iran who complained left hemiparesis and was diagnosed Moyamoya disease by brain and cervical CT-Angiography. There was still great difficulty in the diagnosis of diffuse white matter lesions. The CT-Angiography showed bilateral internal carotid stenosis with "puff of smoke" collateralization arising from the circle of Willis, therefore Moyamoya disease was raised. The clinical diagnosis of Moyamoya is challenging and misdiagnosis is probable. Therefore, the physicians should know this disease and think about it in patients with Juvenile stroke. This shows that Moyamoya disease should be considered in differential diagnoses especially among young patients presenting with unexplained cerebrovascular syndromes.