Three scenarios are presented, based on real patients, illustrating various clinical dilemmas involving critical illness and extracorporeal membrane oxygenation (ECMO). The scenarios are outlined in the form of questions and answers. In most cases there is no single correct answer to the dilemmas presented. The pros and cons of particular interventions are discussed along with the actual treatment provided. In all cases, the ECMO circuit consisted of a polymethylpentene oxygenator (Quadrox PLS; MAQUET Cardiovascular, Hirlingen, Germany) and a centrifugal pump (Rotaflow; MAQUET Cardiovascular). Case 2 has been previously published as a letter to the editor (1).