The importance of subjective health measures has increased over the recent years. Prevention of acute and chronic diseases and early intervention in children depend upon availability of measures that can be routinely used for monitoring purposes. Traditional outcome measures (survival, laboratory tests) have limited value when assessing health status of chronically ill persons or screening population. Research on quality of life has a solid methodological background. High importance is attached to psychometric characteristics of developed questionnaires. However, only a few (especially generic) instruments have been developed for children and youth. The aim of the study is: 1) to describe the main concepts and methods in quality of life research in relation to paediatric practice; 2) to present the KIDSCREEN project sponsored by European Commission, currently in progress. The KIDSCREEN multicenter project is being developed by 13 European countries, including Poland, within the 5th Framework Programme Quality of Life and Management of Living Resources. The project will provide the opportunity to measure the HRQL in children and adolescents across different countries and cultures using a standardized multidimensional instrument developed at the same time in all participating countries. It is expected that it will improve medical, psychological and educational care of children and adolescents and will be very useful in changing the system of preventive health care provided in Polish schools. Applying the KIDSCREEN questionnaire in selected EU candidate countries will anticipate the problems that could affect other countries in the same economic situation.