The prison population experiences significant health inequality and social exclusion (Department of Health 2002). Once incarcerated, prisoners are at increased risk of mental illness and have higher exposure to communicable diseases (WHO 2008). Prisoners generally have poorer health because imprisonment negatively impacts upon the health of the individual (WHO 2008). However, the prison setting offers a unique opportunity to implement targeted health promotion initiatives with a population that may have had very limited experience of accessing health services prior to incarceration. The World Health Organisation recognises the need for health promotion in prisons. This is evidenced in the Health in Prisons Project (HIPP), the aim of which is to support member states in improving health and health care in prisons, and to facilitate the links between prison health and public health systems at both national and international levels. In practice however, implementation of the HIPP is complex. This paper examines the challenges in promoting health in prisons globally and in Irish prisons specifically, given that the prison setting is omitted from the Irish National Health Promotion Strategy. Based on a qualitative research design that incorporated semi-structured interviews with a purposive sample of twelve leading figures in prison policy in Ireland, this paper discusses the need for health promotion interventions in Irish prisons. The paper also discusses the influence of organisational culture on attitudes of prison staff towards engaging in health promotion with prisoners and explores the problems posed by lack of national policy and funding for health promotion initiatives in the prison setting.