Adequate law regulations specify conditions under which mentally disordered persons may be submitted to physical restraint. Medical staff who decide on the application of physical restraint play the role of police. They limit the liberty of mentally disordered persons to protect society against their dangerous behaviour. Protection of patients' health gives the possibility of using physical restraint on the basis of medical circumstances. A literature review shows the different range of physical restraint use in comparable medical units. It suggests that medical staff decisions about the use of physical restraint can be dependent not only on dangerous behaviour but on different specific and non-specific factors. The aim of this article is to analyse factors which can have influence on applying of physical restraint in mentally disordered persons. Description of specific circumstances in which physical restraint is used can help in the optimization of psychiatric treatment and requires further research in both psychiatry and law.