Health care in prison is a challenging task. The conditions of imprisonment create distinct difficulties for those providing health care in this setting. These particular circumstances have led to a shortage of quality professionals, working for the health of imprisoned people. The aim of this study is to elaborate reasons for healthcare professionals to work in a prison environment. The main research question is: why do healthcare workers choose to work in prisons? Furthermore, our study identifies training needs in various fields. Interview data that comes from a national project carried out in Switzerland and three other relatively wealthy countries were analyzed using content analysis. One-on-one, semi structured interviews were designed and conducted with professionals working in prison context. A total of 105 interviews were carried out and for this work 83 of them were analyzed and coded into themes responding to the study aim. Most participants chose to work in prison either because of practical reasons, as many reported various forms of contact with the studied prison environment at a younger age, or because of intrinsic reasons, including among others, having the wish to change the system of healthcare in prisons. Even though the education of the participants varied greatly, a lack of specialist training was expressed by many health care professions as an important factor. This study points out the need for more specific training programs for healthcare workers in prison and provides suggestions to ameliorate the recruitment and education for future prison health care workers.