Involuntary hospitalization for treatment of mental patients is a necessity in modern scientific psychiatric practice. Hospitalization is generally an act of psychological and social disruption of individual's homeostasis, which is a very important and complex problem for the mentally ill. The goal of the study was to confirm the necessity of involuntary treatment of mental patients in a medical institution, in the interest of patients and the society. The research was conducted as a cross sectional study of hospitalized patients in 2012 at the Clinic for psychiatric disorders "Dr Laza Lazarevic" in Belgrade. It included 2286 inpatients, especially involuntarily hospitalized 236 and 719 admitted for hospital treatment with the assistance of the police. The data were statistically analysed by methods of descriptive statistics: χ2 -test and multiple logistic regression analysis, using the software package SPSS v. 20. The results show that 255 patients were admitted to the hospital for the first time with the assistance of the police. Patients hospitalized with the assistance of the police in compared to those hospitalized without the assistance of the police were, with statistical significance: younger, more frequently males, most frequently in the diagnostic group of schizophrenia and less frequently in the group of organic and affective disorders, most often it was their first, and involuntary hospitalization. During the studied period, 236 (10%) of the total number treated patients were involuntarily hospitalized. There were 176 (74.58%) patients detained for treatment by force, with the assistance of police. There is a necessity for involuntary hospitalization of mental patients. The justification of detaining patients in the health institution by such measures is accomplished through legislation in the best interest of the patient.