We report our experience using an originally designed thin walled metal-tipped arterial cannula for neonatal open heart surgery. Its external diameter is 2.1 mm and its internal diameter is 1.7 mm, it has a high internal – external diameter ratio. It was used on 36 patients, who were either neonates or small infants. In 32 of the patients, it was inserted into the ascending aorta for systemic perfusion. In the other 4, it was inserted into the brachiocephalic artery for selective cerebral perfusion during repair of the aortic arch. The relationship between the pressure drop and the bypass flow was obtained for the 7 most recently treated patients. The pressure drop at a bypass flow of 500 ml/min was 150 mmHg. Due to the high internal – external diameter ratio of this cannula, and its excellent flow characteristics, we consider it to be particularly useful in neonatal open heart surgery, while it also allows for successful selective cerebral perfusion during repair of the aortic arch in neonates.