In the last 5–10 years, the population of children and newborns admitted to Paediatric and Neonatal Intensive Care Units has changed rapidly, often due to achievements in areas of medicine beyond the ICU. For example, developments in genetic modulation on an individual basis now bring children to the ICU who were once considered non-salvageable for whom intensive care treatment was considered futile. Technological changes in extracorporeal support, which can now be provided for prolonged periods, equally contribute to this changing landscape of admitted patients. Long-term follow-up is nowadays considered a pivotal part of the evaluation of specific treatments and of PICU care itself, with a need to follow up children admitted into PICU into adolescence and even adulthood to provide relevant outcome results.