Objectives: Currently there is a lack of information regarding the health-related quality of life (HRQoL) of healthy as well as chronically ill children on a European level. In 2 European projects questionnaires for the assessment of the HRQoL in children and adolescents have been developed: The KIDSCREEN project aims at a co-operative European development of a standardised screening instrument for children's HRQoL for the implementation in representative national and European health surveys. In the DISABKIDS project a chronic-generic questionnaire as well as modules for specific conditions (e.g. asthma) were developed for children with chronic conditions.

Methods: Both projects shared similar steps: 1. Development phase, in which the items were generated and tested, 2. Survey and Field phase, in which the modified questionnaires were tested with healthy and chronically ill children and adolescents in national representative surveys, and 3. Implementation phase in national health surveys or clinical studies.

Results: In the sister projects, the KIDSCREEN instrument was tested in 22,830 children and the DISABKIDS instrument in 1605 chronically ill children. The current paper describes the development and pilot-testing as well as psychometric results of the field tests of both studies.

Conclusion: The KIDSCREEN/DISABKIDS instruments make it possible to assess generic, chronic-generic and disease-specific aspects of quality of life in children and present an innovative approach to intercultural HRQoL assessment in health research.