Optional Protocol in the past decade, as a global system for preventing torture and other forms of ill-treatment, allows access for external and independent control, international organizations and national authorities to the places in which are placed persons deprived of their liberty. The fact that the Subcommittee on Prevention of Torture and the national mechanisms have the power to access any place where persons are deprived of their liberty serve as a deterrent against ill-treatment, increases transparency and promote responsibility for acts of torture and abuse.

More than 60 countries have established their National Preventive mechanisms. The Republic of Serbia has signed the Optional Protocol in 2003 and on 28 July 2011 at the session of the National Assembly of the Republic of Serbia Ombudsman is designated to perform duties of the National Preventive Mechanism (NPM) in cooperation with ombudsmen autonomous regions and associations whose statute provided objective of association is promotion and protection of human rights and freedoms.  
NPM Serbia in its work so far carried out 350 visits to places where persons deprived of their liberty are or may be placed and addressed over 1000 recommendations for removal of the identified deficiencies. Encourages the impression that the authorities responsible for the direct treatment of persons deprived of their liberty prevails awareness of the necessity to eradicate ill-treatment and torture, and that with the Ombudsman in the performance of NPM realized prescribed cooperation, that have been taken measures for most of the sent recommendations, which all lead to a significant change in the general attitude of the public on the prohibition of torture, but also to numerous examples of improving the treatment of persons deprived of their liberty.
The Optional Protocol to the UN Convention against Torture (OPCAT) was adopted in December 2002 by the UN General Assembly and entered into force on 22 June 2006. Currently, 81 countries from around the world has ratified or acceded to the Optional Protocol, 17 countries have signed it, and many are in the process of accession.