Nina Klang (2012): Applicability of the ICF-CY to describe functioning and environment of children with disabilities. Studies from the Swedish Institute for Disability Research 41, 83 pp. The aim of the thesis, with four empirical studies, was to explore the applicability of the International Classification of Functioning, Disability and Health, version for children and youth (ICF-CY) to describe functioning and environment of children with disabilities. The components and categories in the ICF-CY were explored by studying items in ICF-CY based questionnaires in studies I and II and by linking texts of individual habilitation plans to the ICF-CY in studies III and IV. Professionals’ perceptions of the applicability of the ICF-CY and the ICFCY questionnaire were investigated in study II. In study IV changes in focus on ICF-CY components in documentation of individual habilitation plans were explored after in-service training in the ICF-CY. Studies I and II found variations in ratings of questionnaire items based on the performance qualifier in component Activities and participation. The variations may be explained by the context in which ratings were made and by expectations and perceptions of those who made ratings. The results indicated challenges in constructing universal measures of the performance qualifier. The studies also indicated limitations in the use of items based on Environmental factors, when used separately from items in Activities and participation. Studies II and III found that the categories in the components Body functions and Activities and participation were interrelated. Study III indicated challenges in describing family situation and children’s psychosocial environment in the Environmental factors. In study II the professionals described advantages and challenges in the use of the ICFCY and suggested necessary changes to the ICF-CY questionnaire. Study IV found that the professionals in child and youth habilitation described children’s functioning more precisely and in more detail after in-service training. Overall, the results suggest both advantages and challenges of the ICFCY when used to describe functioning and environment of children with disabilities. The results call for a need of a combined use of the categories from all the ICF-CY the components.