<p dir="ltr">The project follows an adapted version of the James Lind Alliance (JLA) Priority Setting Partnership (PSP) approach. It is led by a multidisciplinary project team of paediatric experts and methodologists, in close collaboration with key stakeholders. The main project stages are: <i>1) Gathering uncertainties</i> via a survey of paediatric experts and methodologists, and qualitative consultation with families, supplemented with an existing list already harvested from the literature. This results in a long-list of challenge and barriers to paediatric trials. <i>2) Verifying uncertainties</i><b> </b>by removing out-of-scope items, grouping in-scope items into themes, and creating summary questions that are then checked against existing methods to confirm genuine gaps. <i>3) Interim priority setting</i><b> </b>where all stakeholders are invited to review the list and select up to 10 priorities through a national, online survey. <i>4) Final priority setting</i> to identify the ultimate Top10 priorities. This is through a consensus workshop with shared decision-making between paediatric experts, methodologists and families, using an adapted Delphi meeting approach.</p><p dir="ltr"><b>The present document lists the long-list of resulting clusters from the Stage 1 survey, and Stage 2 verification. This is in parallel with the interim priority setting, and separately from the ultimate, resulting overall publication.</b></p>