Significant advances have been made in extracorporeal life support, which has resulted in the increased use of post-cardiotomy extracorporeal membrane oxygenation. Retrospective studies have contributed to the ongoing evolution of selection criteria for post-cardiotomy extracorporeal membrane oxygenation. Current indications include failure to wean from cardiopulmonary bypass, haemodynamic collapse, pulmonary hypertension, post-repair of hypoplastic left heart syndrome, or need for bridge to transplantation. Short- and mid-term results are improving. Ethical concerns still attend the process, however. Moral risks related to post-cardiotomy extracorporeal membrane oxygenation may be encountered before, during, and after the open heart procedure. At each stage of the decision-making process, moral risks are encountered by many factors that may result in decisions that may be contrary to the best interests of the patient, parents, or use of shared societal resources. These moral risks centre around the selection process, informed consent, decision making in the operating room, and post-operative maintenance of extracorporeal membrane oxygenation. Consideration of such risks is affected by questions of haemodynamic stability, haematologic compromise, neurologic status, and family concerns. We conclude that thorough understanding of the relevant scientific literature, heightened awareness of moral risks, and incorporation of ethical tenets in clinical deliberation will guide the clinician to do the right thing.