Psycho-oncology cares for patients and families in times of acute existential crises. The treatment deals with the difficult issues surrounding illness, often on the way to death. One should not be surprised that it often leads to an entanglement of psychopathology, dysfunctional responses, and ethical dilemmas. This chapter defines boundaries in psycho-oncology, and discusses the severely ill patient, whose sense of self, already threatened by cancer, may be further threatened by the modern medical care experience. The chapter thendescribes how psycho-oncology and ethics are intertwined, and what tools psycho-oncologists can use to clarify, improve, and, if possible, resolve them. Making “a situational diagnosis” requires a more exhaustive analysis than do the simpler cases, and often provides a better resolution of ethical problems that were entangled with disease management. Together, they help achieve the chapter’s fundamental goal, namely emphasizing ways of sustaining the patient’s personhood during an often brutal ordeal.