This chapter discusses the evaluation of quality of life (QoL) measures in children and adolescents, focusing on four main research questions: the extent to which adult measures are used in evaluating healthcare interventions in children, the appropriateness of adult measures for children, the correspondence between child self-reports and assessments by parents and carers, and the feasibility and reliability of proxy measures of QoL in different disease contexts. The chapter highlights the importance of QoL in pediatric practice, particularly in evaluating the impact of treatments and interventions. It reviews the literature on QoL measures, noting the lack of consensus on definitions and the need for more comprehensive and child-specific measures. The chapter also emphasizes the need for QoL measures to reflect the child's perspective and to be sensitive to changes in their quality of life. Finally, it discusses the epidemiology of chronic diseases and the changing landscape of childhood illness, highlighting the need for outcome measures that reflect a holistic approach to management and recognize the side effects of treatments.This chapter discusses the evaluation of quality of life (QoL) measures in children and adolescents, focusing on four main research questions: the extent to which adult measures are used in evaluating healthcare interventions in children, the appropriateness of adult measures for children, the correspondence between child self-reports and assessments by parents and carers, and the feasibility and reliability of proxy measures of QoL in different disease contexts. The chapter highlights the importance of QoL in pediatric practice, particularly in evaluating the impact of treatments and interventions. It reviews the literature on QoL measures, noting the lack of consensus on definitions and the need for more comprehensive and child-specific measures. The chapter also emphasizes the need for QoL measures to reflect the child's perspective and to be sensitive to changes in their quality of life. Finally, it discusses the epidemiology of chronic diseases and the changing landscape of childhood illness, highlighting the need for outcome measures that reflect a holistic approach to management and recognize the side effects of treatments.