The cost of treatment of mentally ill patients is taking an ever more important place in the health care systems of many countries. This is caused by an increasing interest of the taxpayers who want to know where their money goes in relation to medical expenses. It is logical that taxpayers' expectations include improvement of the health care system. Medicine cannot be considered in the category of a profit making economy because some of the fields of medicine are not and cannot be profitable. At the borderline between economy and medicine, pharmaco-economy was born. This new science considers the cost of treatment of various sicknesses; furthermore it tests the comparative costs and the use of pharmaceutical products. In pharmaco-economy we distinguish three different types of costs: the continuous cost (consequent to medical treatment), the indirect cost (related to losses on support of patients and their family members), the unassessable cost (psychological losses). A correct economical analysis is multi-factual and refers to different sides of our lives. With this understanding we can only consider the general economical results, that is, the so called "economical treatment result". It is believed that this way of thinking can cause an intensive development in the rehabilitation of chronic mentally ill patients in Poland. This rehabilitation can be a classical example of modern economy: hypothetically high initial costs cause their substantial reduction in the progressive development of the programme until they reach their effective reduction at the end, i.e. the progressive improvement of the patients functioning within their natural environment.