The prohibition of cruel, inhuman and degrading treatment and punishment is the only absolute right which makes the common denominator of all international documents that deal with the field of fundamental human rights. In certain places in this doctoral thesis for simpler expression, these terms in wider sense I mark also with the words „torture“ or „ill-treatment“. The conducted research which makes the core of this paper was exactly to establish manifestation of torture (in wider sense) in the Republic of Croatia towards persons deprived of their liberty, from their own point of view. After introductory part which is contained of introductory considerations and brief content of chapters and used methodology, I give a review of forms, methods and frequency of the use of torture throughout history. Then, the analysis of international legal sources regarding prohibition of cruel, inhuman and degrading treatment and punishment is made, among which also ones of international humanitarian law as well as domestic legal sources. Comparative law review follows. I have analysed experience of United States of America as well as Republic of Germany as those were the countries with different approach to the protection of human rights. Ater general remark regarding definition of terms torture, cruel, inhuman and degrading treatment, I analyse these terms according to United Nation's Convention against torture, cruel, inhuman and degrading punishment and treatments as well as according to European convention of human rights and fundamental freedoms. Not only analysis of negative and positive obligations of the States according to Article 3. is being given, then also essential standards that European Court of Human Rights (futher ECtHR) applies in connection to Article 3. Furthermore, I have analysed the case law of the Constitutional Court of the Republic of Croatia which refers to inhuman and degrading treatment of persons deprived of their liberty according to applied standards, with special emphasis to the introduction of a new legal remedy – constitutional complaint in cases of inefficient investigation. Moreover, I have also analysed available legal remedies in Republic of Croatia in the cases of cruel, inhuman and degrading treatments well as their efficiency, by obtaining statistical data of the competent bodies. The analysis of the case-law of execution judges regarding requests for Court's protection in the period from 2010 -2020 is being given. The core of the paper makes empirical research conducted by directly surveying the targeted group – persons deprived of their liberty, a total of 266 respondents, which research represents the first such research in the Republic of Croatia. The paper confirmed the hypothesis that in the Republic of Croatia, the rights of persons deprived of their liberty are, to a significant extent, not being respected in accordance with the standards of the ECtHR. The results of the research justify the thesis that there is a high number of human rights violations of persons deprived of their liberty, in which the appropriate procedure for their remediation has not been carried out. Manifestation forms of the violation of prohibition of torture, inhuman and degrading treatment are extorting confessions and disciplining the disobedient in an unlawful manner, but not in equal proportion, as it was set out in the second hypothesis of the research. As it will be reasoned in detail, the number of “other” motives from which, as the prisoners believe, such behaviour occurs, is surprising and amounts to as much as 70%. The existing legislative framework, although well set-out in the substantive law, is way too dispersed, unclear, inadequate and ineffective. In the chapter “Concluding remarks and proposals de lege ferenda” I present proposals for legislative amendments which are the outcome of the overall analysed experience of other countries and shortcomings which were established in the analysis of the Croatian experience. The aim of this paper is being achieved by the proposal how to establish an effective legislative framework which would, applied in practice, prevent inhuman and degrading treatment and punishment pro future, that is, which would reduce its application to a minimum