Pulmonary atresia with intact ventricular septum is a complex cyanotic congenital heart lesion with the potential for myocardial ischaemia due to the presence of coronary artery anomalies. We present a case of a two-day-old baby with postnatal diagnosis of pulmonary atresia with intact ventricular septum in whom non-invasive ferumoxytol-enhanced 4D cardiac magnetic resonance angiography was used for the assessment of coronary artery anatomy.