For the ethical evaluation of psychiatric decisions the will of the patient--apart from his welfare, of course--has gained special importance in recent years. It is constitutionally protected in the form of self-determination. Accordingly the physician can only act with the patient's consent. The capacity of the individual to consent may be impaired or suspended because of a mental disease. It is often difficult, however, to recognize this impairment, to assess its extent, to evaluate its current relevance and to draw the correct conclusions. This becomes important when the psychiatrist deals with a patient whose will is in opposition to his welfare. Difficulties for the physician may also result because his therapy, regardless of whether it is somatic therapy or psychotherapy or involves social measures, though aiming to remove the mental disturbance and with the ultimate objective of the patient regaining his lost autonomy in mind, may at times curtail the self-determination of the patient. These difficulties are illustrated by some examples with the objective to maintain our awareness of these issues in our everyday work.