This thesis follows the paper based format in that Papers One and Two are stand-alone papers prepared for submission for Clinical Child and Family Psychology Review and the Journal of Clinical Child and Adolescent Psychology respectively. The relevant submission guidelines are included in the appendix (Appendix 1). Asthma is the most common childhood chronic illness affecting an estimated 1.1 million children in the UK. A substantial body of research has shown that asthma prevalence and morbidity rates are associated not only with physiological factors but also with environmental and psychosocial factors. Identifying modifiable psychosocial variables involved in the expression and outcome of asthma in children enables identification of how and where interventions could be targeted. Two papers are presented in this thesis, which aims at contribute to research in this area followed by a critical evaluation of the research process, relevance and implications of the presented papers.Paper One is a review of the literature highlighting the biopsychosocial variables involved in the onset and development of childhood asthma. A model is proposed which aims at demonstrate the bidirectional influence of many variables thought to be involved in paediatric asthma expression. One significant area within the literature highlights the extent to which behaviour problems are elevated in asthmatic children. The prognosis for children who develop significant behaviour difficulties is poor.Research has shown that the quality of parenting a child receives has a significant impact on both the child's well-being and development. Literature included in Paper One highlights the relationship between asthma and parenting. Caregivers of asthmatic children have been shown to be more hostile and critical compared with caregivers of non-asthmatic children.Intervening early with families to promote warm, consistent and positive parenting is considered one of the most effective ways to treat behaviour difficulties. Parent training programmes have emerged as the most efficacious method of intervening with and treating child behaviour difficulties and enhancing parenting skills. In spite of their demonstrated effectiveness, engagement with programmes is often poor. As a result researchers have developed self-directed and web-based interventions. Despite their apparent benefits, uptake and continued engagement remains low.Paper Two aimed at examine whether providing asthma specific information enhanced engagement with a Triple P web-based intervention and identify any pre-treatment variables that predicted engagement. The final section, the Critical Evaluation, aimed at place the research in the wider context, consider the findings from both papers, highlight additional and unexpected outcomes and discuss the implications for future studies and limitations of the thesis.