Background: Improvements in cystic fibrosis (CF) treatment over the last two decades have brought large increases in life expectancy. As a result, researchers have become more interested in the long-term quality of life and psychological wellbeing of adults with CF. Introduction of segregation policies to prevent cross-infection have added a new dimension to life with CF; patients are discouraged from meeting face-to-face and this impacts on access to peer support. Systematic review: A systematic search of the published literature since 1990 identified 10 journal articles describing research with adolescents and adults with CF, their mental health needs and social support or functioning. Quantitative papers indicated an inverse relationship between mental health and social support or social functioning. Objectives: The internet has become increasingly used for social networking and accessing social support resources. This thesis aimed to explore the psychological wellbeing of adults with CF who make use of online social support and the themes emerging within online discussion forums. Method: Study 1 is a quantitative survey carried out online which assesses the quality of life, mental health and self-esteem of 74 adults with CF. Study 2 uses framework analysis to provide a qualitative exploration of posts made by participants on an online discussion forum. Results: Moderate levels of quality of life and comparably high levels of self-esteem were found. Thirty per cent of the sample population scored above threshold for clinical levels of mental health difficulty. Significant correlations indicated that poorer self-esteem was associated with poorer quality of life and greater mental health difficulty. Six themes emerged from the discussion forum posts including CF treatment, daily living and occupation, health exacerbations, psychosocial processes and issues and the future. Conclusions: Self-esteem and mental health scores were similar to previous research. However, quality of life was noted to be considerably lower when compared to other research samples. This was thought to be influenced by the overrepresentation of females in the current sample but may also be reflective of the group of people with CF who make use of online resources. Results are discussed in relation to clinical implications, limitations and directions for future research, including the efficacy of internet groups in improving wellbeing and consideration of possible developments in technology to promote socialisation in the CF population.