This paper deals with psychiatric diagnoses. Benefits and disadvantages associated with making a diagnosis are discussed, as well as problems which appear in connection with the classification of mental disorders. Diagnoses always are influenced by the model of health and illness which forms the basis. They are no firm constructs, but modified during time and by social transformations. From time to time there are accumulations of certain diagnoses. In the process of therapy, diagnoses serve activating knowledge among professionals and patients, offering instructions as well as supporting multidisciplinary communication. Nevertheless, the reliability of psychiatric diagnostics is insufficient. For the patient, a diagnosis is connected with numerous emotional effects and the danger of stigma and social exclusion. Hence, a diagnosis should be always used as a temporary hypothesis which is checked and steadily adapted in a circular process. Psychiatry social work should always regard diagnoses in a critical way and make an effort to recognize a patient as entire person. For social work it is necessary to reflect its own skills in the multidisciplinary setting and argue for them more efficiently to encourage professional identity.