In recent decades, psychiatric ethics has been an area of intensive research and reconsideration of established regulations. Basic principles of medical deontology do not cover ethical issues of modern psychiatric science and practice. The fundamental principle of ethical relationship between a physician and a patient in psychiatric practice is a voluntary informed consent that is based on three main criteria: voluntarism, decision-making capacity and information disclosure about proposed medical procedure. The principle of voluntary informed consent implies a dialogue between a psychiatrist and a patient that rely on the principles of patient’s autonomy and does not allow the priority of the paternalistic approach. The physician is obliged to provide all available information on the proposed intervention in a comprehensive way and assess the degree of patient’s awareness of this information. The main objective is to determine patient’s ability to make decisions as accurately as possible. Many mental disorders affect cognitive processes of decision making and may impact patient’s autonomy. It is unacceptable to consider psychiatric patients as incapable of making decisions in advance.