This thesis focuses on the exploration of young adults' experience of having a parent with Young-onset Dementia (YOD). In particular, their experience of the developmental tasks typically associated with young adulthood and their understanding of changes within family roles and relationships in view of their parent's illness were investigated. Previous research examining parental illness has not yet fully examined the young adult cohort as a distinct group, focusing on the experiences of adolescents and younger children instead. There is also an absence of YOD as a specific form of parental illness within the literature. Previous studies have also typically used quantitative methods to gain retrospective or parental accounts of younger people's coping and burden as a result of parental illness and there is little understanding of the current experiences of younger people. As an exploratory study, this thesis used qualitative methods. Five young adults (aged between 23 and 37) were interviewed about their experiences, and their transcripts were analysed with Interpretative Phenomenological Analysis -IPA (Smith, 1995). Four super-ordinate themes emerged within the analysis of group themes. These were: Experiencing change in relationships, Understanding Change, Managing Change and Experiencing change in self. The analysis also revealed that participants had a range of experiences of the interview process itself. The findings indicate that completion of the developmental tasks of young adulthood and family roles and relationships are affected by having a parent with YOD, and clinical implications are discussed in view of the distressing nature of changes experienced. Recommendations for future research include investigating the various moderators that seemingly impact on young adults' experiences of parental YOD and an exploration of clinical interventions that would be most efficacious with this cohort.