The World Health Organization (WHO) defines participation as a person’s involvement in a life situation, and to participate in leisure activities is one of the most important aspects of health and well-being. When a child is involved and engaged in a leisure activity, it gives the child a sense of belonging, opportunities to make friendships, and possibilities to develop physical and social competences and skills. Children with disabilities tend to be restricted in their abilities to participate in leisure activities due to mobility problems, communication disorders, and pain, but also as a result of negative attitudes from others and problems with transportation and accessibility.Knowledge of the personal and environmental factors that facilitate or hinder participation in leisure activities for children with disabilities is essential to be able to implement successful interventions with the aim of increasing participation. This requires a valid assessment of participation that can give both an objective and subjective view of the multidimensional construct.The overall aim of this doctoral thesis is to describe and compare patterns of participation in leisure activities of children with and without disabilities by cultural validation and use of the Children’s Assessment of Participation and Enjoyment/Preferences for Activities of Children (CAPE/PAC) in the Swedish context. A specific goal is to develop and implement a client-centred model of intervention with the aim of improving participation in leisure activities by children with disabilities.The result from Study I showed that the slightly modified Swedish version of the CAPE was valid for Swedish children. The outcome of standardized mean diversity score was significantly higher compared with the outcome of the original version of the CAPE, indicating that validation of the item relevance in the new context was necessary. The overall findings in Study II indicated that Swedish children with disabilities participated in a higher diversity of leisure activities, but with less intensity, compared to children without disabilities. Study III showed that there are differences between countries in patterns of participation in leisure activities for children with disabilities in regards to both diversity and intensity. For children without disabilities there were only minor differences between the countries. The results of Study IV showed that a designed intervention approach could be applied in the clinic for increasing participation in leisure activities by children with neuropsychiatric diagnosis.The overall clinical implications and conclusions from this thesis are three-fold. First, a cultural validation of the CAPE/PAC is necessary when surveying Swedish children’s participation in leisure activities. Second, the patterns of participation in leisure activities of children with and without disabilities differ both nationally and internationally, and this provide evidence of the need for changes in national legislations, policies, and therapeutic approaches that promote participation of children with disabilities. Third, an intervention model with a client-centred approach in which children with disabilities define their own leisure activity goals by using the CAPE and PAC appears to be effective in increasing participation in leisure activities.