BACKGROUND: The number of children who require palliative care has been estimated to be as high as 21 million globally. Delivering effective children's palliative care (CPC) services requires accurate population-level information on current and future CPC need, but quantifying need is hampered by challenges in defining the population in need, and by limited available data. The objective of this paper is to summarise how population-level CPC need is defined, and quantified, in the literature. METHODS: Scoping review performed in line with Joanna Briggs Institute methodology for scoping reviews and PRISMA-ScR guidelines. Six online databases (CINAHL, Cochrane Library, EMBASE, Medline, PsycINFO, and Web of Science), and grey literature, were searched. INCLUSION CRITERIA: literature published in English; 2008-2023 (Oct); including children aged 0-19 years; focused on defining and/or quantifying population-level need for palliative care. RESULTS: Three thousand five hundred seventy-eight titles and abstracts initially reviewed, of which, 176 full-text studies were assessed for eligibility. Overall, 51 met the inclusion criteria for this scoping review. No universal agreement identified on how CPC need was defined in population-level policy and planning discussions. In practice, four key definitions of CPC need were found to be commonly applied in quantifying population-level need: (1) ACT/RCPCH (Association for Children with Life-Threatening or Terminal Conditions and their Families, and the Royal College of Paediatrics and Child Health) groups; (2) The 'Directory' of Life-Limiting Conditions; (3) 'List of Life-Limiting Conditions'; and (4) 'Complex Chronic Conditions'. In most cases, variations in data availability drove the methods used to quantify population-level CPC need and only a small proportion of articles incorporated measures of complexity of CPC need. CONCLUSION: Overall, greater consistency in how CPC need is defined for policy and planning at a population-level is important, but with sufficient flexibility to allow for regional variations in epidemiology, demographics, and service availability. Improvements in routine data collection of a wide range of care complexity factors could facilitate estimation of population-level CPC need and ensure greater alignment with how need for CPC is defined at the individual-level in the clinical setting.