The overall aim of this thesis was to develop knowledge about how to promote health in children treated for cancer and how health promotion interventions based on such knowledge can be evaluated. In this thesis, a descriptive and explorative design has been used, comprising both qualitative (Papers I-III) and quantitative (Papers I and IV) methods. A nationwide cohort of 144 childhood cancer survivors (24-42 years) answered a questionnaire about the support they had received from health care services (Paper I). Fifteen children (8-12years), with experience of cancer treatment, participated in five focus groups with two sessions per group (Paper II and III). The focus group methodology was combined with participatory and art-based techniques, such as draw and tell and photography. The children discussed what promotes health and what friendship is about. A methodological design was used to psychometrically test the Swedish version of the Minneapolis-Manchester Quality of Life instrument (MMQL) (Paper IV). The study included 950 pupils in grade 6 and 9 from seven primary schools. In addition to this, a comparison of the MMQL instrument with the health-promoting factors described by children in the focus groups was performed.

The findings showed that there is a need for health-promoting factors, such as knowledge and psychosocial support, from health care services for childhood cancer survivors. Their family and friends may contribute with support and then serve as health-promoting factors. Health-promoting factors, according to children 8-12 years of age and with experience of cancer treatment, are meaningful relationships, recreational activities and a trustful environment. The children expressed a holistic view of what promotes their health. Friendship, from the perspective of the children, is a process of equal and mutual commitment that develops over time and with interactions occurring face-to-face and digitally. The MMQL instrument may be valid and reliable in a sample of healthy children. However, less than one-third of the items in the MMQL instrument could be linked to the health-promoting factors that the children participating in the focus groups highlighted. In conclusion, the findings in this thesis contribute knowledge from a participant perspective regarding the needs and the experiences of health-promoting factors for those who have received treatment for cancer. This knowledge could form a basis for development of health promotion interventions aimed at children who have received treatment for cancer. It is suggested that if the MMQL instrument is used to evaluate health promotion among children who have received treatment for cancer, the MMQL should be complemented with items that capture aspects of health that are important to the children.