© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ. Clinical trials of xenotransplantation (XTx) may begin early in the next decade, with kidneys from genetically modified pigs transplanted into adult humans. If successful, transplanting pig hearts into children with advanced heart failure may be the next step. Typically, clinical trials have a specified end date, and participants are aware of the amount of time they will be in the study. This is not so with XTx. The current ethical consensus is that XTx recipients must consent to lifelong monitoring. While this presents challenges to the right to withdraw in the adult population, additional and unanswered questions also linger in the paediatric population. In paediatric XTx, parents or guardians consent not only to the initial treatment of the child but also to lifelong monitoring, thus making a decision whose consequences will remain present as the child develops the capacity for assent, and finally the capacity for informed consent or refusal. This article presents and evaluates unanswered paediatric ethical questions in regard to the right to withdraw from XTx follow-up in the paediatric population.