Veno-arterial extra-corporeal membrane oxygenation (VA ECMO) in children is often established by cannulation of the right carotid artery and the right internal jugular vein. Cerebral infarction which is sometimes seen in such cases may be secondary to an incomplete circle of Willis. We present 3 cases with VA ECMO using cervical cannulation who suffered cerebral infarction which may be attributed to an incomplete circle of Willis.