This three-stage study led to the development of a delineation model of occupational therapy practice for children with Attention Deficit Hyperactivity Disorder (ADHD). Stage one explored the current practice of occupational therapy in the United Kingdom (UK) by conducting a national survey of 282 paediatric occupational therapists. Results indicated that there were only a small number of occupational therapists (8.5%) working in a designated service for children with ADBD. This result suggested that occupational therapy for children with ADHD is a small field of practice. Stage two involved the consensus development on the role of occupational therapy for children with ADHD. Seventy-two paediatric occupational therapists participated in the study. The therapists' top six priorities of assessment and five priorities of intervention were identified. An occupational therapy delineation model of practice was developed by integrating data generated from this research, information from the literature review, and the author's clinical experience. In order to apply the model to clinical practice, a family-centred occupational therapy care package was developed. The third stage evaluated the process and outcome of the devised care package by conducting a multi-centred efficacy study. Twenty occupational therapists from the four countries in the UK attended a 3-day course to learn to implement the care package. Following their training, they submitted data on a sample of 20 children with ADHD. The majority of these children (85%) showed improvement in their behavioural patterns after the implementation of the care package. Over half of the cases (65%) had statistically significant changes of scores in the ADHD Rating Scales. Parents also reported experiencing good family-centred care delivered by the research therapists. The whole study makes a significant contribution to occupational therapy knowledge by creating a new delineation model of practice for which the research undertaken offers some validation.