The aim of the focus groups was to take the perspective of children and adolescents across Europe into account in the development of the statements in the questionnaire. Focus groups consisted of 3 to 6 children were conducted through-out Europe. In addition, focus groups with parents and professionals were carried out as well as in-depth interviews with some children. The groups were classified according to age, type and severity of disease. Standardised operating procedures ensured the compatibility of the results. The group discussions were content analysed to identify the HRQoL themes relevant to children of different ages and with different conditions.