Work Package 1 involved a systematic review, which aimed to identify generic, multidimensional childhood Patient-reported Outcome Measures (PROMs) and synthesise their characteristics by conceptual basis, target age, measurement considerations, and the preference-based value sets that accompany them. PROMs for children (aged 18 years or less) present methodological challenges. PROMs can be categorised by their diverse underlying conceptual bases, including functional, disability and health status; quality of life; and health-related quality of life. Some PROMs are designed to be accompanied by preference weights. PROMs should account for childhood developmental differences by incorporating age-appropriate health/Quality of Life domains, guidance on respondent type(s) and design.