This chapter reviews the measurement of health-related quality of life (HRQOL) and physical function in paediatric pain populations. We present available data on HRQOL and physical function in children with pain, methods of assessment, details about specific questionnaire and performance-based measures, and recommendations for the use of measures based on available evidence. Because many children and adolescents with pain report impairment in participation in physical activities such as walking, running, and sports, physical functioning is a core target and outcome for intervention, particularly for youth with chronic pain. However, the domain of physical functioning encompasses a number of constructs such as physical fitness, physical activity, and subjective disability, which are interrelated, but represent distinct aspects of functioning. Moreover, HRQOL is a broader concept that subsumes physical and psychosocial function. A wide variety of measurement tools are in use, but no guidelines for measurement have been established. A better understanding of measurement of HRQOL and physical function may enable researchers and clinicians to track children’s functional impact and changes in function over time, and to improve the design and testing of potentially effective interventions for children with pain.