The analysis of literature and events in psychiatry in the course Of Past centurie show, that the term mental illness even though it had played a positive role in the development of knowledge of psychic disorders and the place of psychiatry as part of clinical medicine has become an anachronic term in time. Because its content and form were never precisely defined, it began to serve as a means of hiding the lack of knowledge of the causes of mental disorders It was abused against its initial ann, e.g. used to 'label' persons whose behaviour did not fit socially accepted conventions. At times it caused a permanent exclusion of those persons. These circumstances were a means of giving up on the term mental illness in the modern diagnostic-classification systems, Of psychic disorders (DSM-IV, ICD-10). Retaining of the term mental illness, and its derivatives menatlly ill, a mentally ill person are anchronisms in the Polish legislation, which can be a cause of serious misunderstaning's, and abuse. The author believes that these terms should disappear from the Polish legislation and the mental health act. They should be replaced by terms adequate for legal regulations but also be compliant with modern psychiatric terminology.