According to the Polish law, each patient has the right to refuse to consent to a medical procedure, even if the refusal concerns a life-saving procedure. It may be difficult for a physician to accept this kind of decision. In each case, however, medical intervention requires patient’s consent. Its lack makes physician’s actions illegal. Such a situation becomes more complicated when the patient who is intellectually incompetent, unconscious or illiterate is unable to express a consent to a medical procedure. Then, the possibility and the need to document and prove the patient’s consent becomes crucial from the point of view of the legality of medical personnel’s conduct. In this article, two representative clinical cases are discussed in the context of the legal assessment of the physician’s conduct in the event of legal complications related to the process of consenting to medical treatment. The authors analyze ethical dilemmas and legal risks that doctors may face in the process of consenting to risky medical procedures by unconscious and illiterate patient.