The purpose of the article is to reveal four existing models of the National Preventive Mechanism and to highlight the functioning of the National Preventive Mechanism in Ukraine and some other member states of The Council of Europe. On 18th of December 2002 UN General Assembly adopted a resolution # 57/199 which confirmed the Optional Protocol to the United Nations Convention Against Torture and other cruel, inhuman or degrading treatment or punishment. This document was ratified by the twentieth country on 22nd of July 2006 and the same day entered into force. Majority of countries of the world are now trying to reduce the use of torture and other cruel, inhuman or degrading treatment or punishment and to ratify the Optional Protocol to the Convention Against Torture in order to achieve this goal. The authors highlighted four existing models of the National Preventive Mechanism in the world. Special attention is paid to the functioning of the National Preventive Mechanism in Ukraine and some other member states of the Council of Europe. They also paid attention to the fact that in majority of the countries the process of forming and giving functions to NPM is at the stage of formation. Currently, there are countries that have already ratified the Optional Protocol to the UN Convention Against Torture, but for some unspecified reasons have not established an NPM. Such kind of situation is being observed in Europe (Belgium, Finland), Latin America (Brazil, Paraguay, Peru, Uruguay) and Africa (Congo, Guinea, Ghana, South Africa, Togo). In addition, there are countries that have not ratified the Optional Protocol to the UN Convention Against Torture at all, such as the United States of America. As for the existing NPM models, in the authors's opinion, the most successful model is "ombudsman+". This model has a number of positive features, one of which is the ability of the Commissioner for human rights (Ombudsman) to work closely with various organizations and attract specialists from various fields. This makes it possible to conduct more thorough monitoring of places of detention. The Commissioner for Human Rights also has the opportunity to assign certain functions of the NPM to non-governmental organizations that have their own certain authority in society. But this model cannot be considered as ideal, because it also has certain problems that need to be improved. For example, when choosing a non-governmental organization, it is necessary to evaluate the main range of activities of this organization. The organization's participation as a part of civil society in monitoring visits should not be formal, as such a fact may negatively affect the functioning of the NPM.