Basing our clinical study on six typical cases, the different types of psychological responses to the announcement of the treatment options for patients with breast cancer are analysed by their frequency: anxiety with self-control, shunning of reality, questioning, anxiety attack, negation of the diagnosis or negation of the usefulness of the treatment. This classification allows the physician to recognize and analyse better the patient's reactions in order to establish the essential reciprocal trust for their complete observance to the most efficient treatment. Anxiety, linked to the meaning of the word cancer, is the most important component. The different reactions are caused by the patient psychological defenses mechanisms. As for the treatment, the real difficulty is to differentiate anxiety from reactional depression and from true depression. Treatment of anxiety should not be systematic and begins by reassuring the patient with a better patient-physician relationship.