Quality of life (QoL) assessment in children and adolescents needs to be age-appropriate and to address health-related concerns to identify children and adolescents who are at risk from health problems, and to determine the burden imposed by a particular disease or disability. The KIDSCREEN approach has tackled the challenges of international paediatric QoL research by providing measures that are applicable for children and adolescents as well as their parents and that can be used to monitor and evaluate health-related QoL in public-health surveys, in clinical studies, and in research projects. The generic KIDSCREEN questionnaires were developed in the context of a European cross-cultural representative health survey in order to be able to compare health-related QoL across different countries and in order to be able to monitor the health status of children and adolescents. The KIDSCREEN group used a simultaneous approach to develop its cross-cultural instrument, which ensures the cross-cultural applicability of the KIDSCREEN measures, making them both conceptually and linguistically appropriate for use in many different countries. The current handbook describes all relevant user information necessary for applying the KIDSCREEN questionnaires, e.g. psychometrics, norm data for group and individual comparisons, and instructions on how to score the instrument and how to interpret the results.