Cancer is a pressing public health concern which is increasingly associated with a younger population. Individuals aged 25-49 currently account for 9% of annual cancer cases in the UK. With the rise in young adult cancer, the number of dependent children experiencing parental cancer is also increasing. Although an underdeveloped research area, existing evidence suggests loneliness to be central to the experience of adolescents with a parent with cancer. This is concerning as adolescence is a stressful developmental period associated with an increased vulnerability to mental illness. My PhD aims to address the dearth of knowledge surrounding loneliness in adolescence during parental cancer by developing a theoretical model of loneliness in adolescents experiencing parental cancer. This will be achieved using a combination of traditional rigorous research methodologies alongside more novel and participatory methods.