In the field of oncology, the expression can be differently used and recovers various interpretations. Those interpretations reveal the different strategies of medical teams to deal with patients as well as the individual conceptions of caregivers concerning the link between body and mind, and patients' well-being criteria. Whatever is the definition they give of "mental well-being" (feeling good, coping with cancer, etc.), this well-being is wanted by both patients and caregivers because it leads to more comfort in the therapeutic relation and in the day-to-day life. Yet, breaking bad news leads the medical strategies based on hope to failure. This analysis of "mental well-being" as a media of medical representations enlightens the difficulties that remain for medical teams to face illness and death.