Four studies were included in this doctoral dissertation aiming to investigatehow habilitation professionals perceive the ICF-CY in clinical work and to identify everyday life situations specific for children and youth aged 0-17 years. The ICF-CY was the conceptual framework and since the research was conducted on as well as with the ICF-CY, the use of the classification runs like a thread through all the work. The design was primarily qualitative and included descriptive and comparative content analyses. Study I was longitudinal, aiming to explore how an implementation of the ICF-CY in Swedish habilitation services was perceived. Studies II-IV were interrelated, aiming to explore children’s most common everyday life situations. Content in measures of participation, professionals’ perspectives, and external data on parents’ perspectives were linked to the ICF-CY and compared. Mixed methods design bridged the Studies III-IV. Results in Study I indicated that knowledge on the ICF-CY enhanced professionals’ awareness of families’ views of child functioning and pointed to the need for ICF-CY based assessment and intervention methods focusing on child participation in life situations. A first important issue in this respect was to identify everyday life situations. Two sets of ten everyday life situations related to the ICF-CY component Activities and Participation, chapters d3-d9, were compiled and adopted for younger and older children respectively, establishing a difference in context specificity depending on maturity and growing autonomy. Furthermore, key constructs in the ICFCY model were discussed, additional ICF-CY linking rules were presented and suggestions for revisions of the ICF linking rules and the ICF-CY were listed. As the sample of everyday life situations reflects the perspectives of adults, further research has to add the perspective of children and youth. The identified everyday life situations will be the basis for the development of code sets included in a screening tool intended for self- or proxy- report of participation from early childhood through adolescence.