Individuals with Coeliac Disease (CD) are required to follow a strict lifelong gluten-free diet (GFD), however research suggests the approach individuals take to managing the GFD can impact their quality-of-life and psychological wellbeing. Advances in the literature have focused on hypervigilance to the GFD in adults with CD, but there has been a lack of research with children and young people (CYP), whose experience of CD likely differs to that of adults. This thesis aimed to increase understanding of CYP’s approaches to GFD management and improve identification of CYP with hypervigilant approaches. Part One of this portfolio presents a reflexive thematic analysis of CYP with CD interactions and experiences with food. Two themes were generated: need for control over others and the environment; and heightened threat and hypervigilance. The findings were applied to an existing model of gluten-related distress and unhelpful eating patterns developed from research with adults, resulting in an adaptation of the model to reflect the experiences of CYP in the current study. Part Two presents a mixed-methods study to develop and preliminarily validate a CYP version of the Coeliac Disease Food Attitudes and Behaviours Scale (CD-FAB), measuring hypervigilance to the GFD. Content analysis and statistical analysis informed the development of the child CD-FAB, which has good internal reliability, discriminant validity and known groups validity, though convergent validity was limited. Recommendations for clinical and research implications are presented for each paper.