Implementation of medical rehabilitation for children with severe disabilities, arranged by the Social Insurance Institution of Finland, is based on collaboration of the family with several professionals and organizations providing the necessary services. Therefore, it sets special challenges for service provision. Parents' experiences of shared agency and participation during children's rehabilitation process were analyzed in relation to the following research questions: what factors, describing the planning and implementation of rehabilitation, were associated with (a) the parents' satisfaction with planning, (b) the correspondence between the plans and the needs of the child, and (c) the correspondence between the received rehabilitation and the needs and wishes of the child and the parents. A questionnaire survey for the children's parents ("n" = 496) included items on rehabilitation planning and implementation of services. The results were analyzed using cross-tabulations and logistic regression analyses. Taking into account of the parents' and children's preferences in rehabilitation and active participation of the rehabilitation counselor and the therapist were positively associated with parents' satisfaction with planning and the correspondence between the plan and the needs. The rehabilitation process was considered as more successful if the information received was sufficient, the parents were heard in all phases of the process, and the child was motivated to participate. Several stakeholders have responsibilities in medical rehabilitation for individuals with severe disabilities. Parents' experience of good rehabilitation planning in healthcare requires shared agency; that is, rehabilitation professionals listening to the family's preferences in decision making. Parents' experience with a successful rehabilitation process is dependent on information sharing, becoming heard, and collaboration in all phases of the process.