The topic of this master's thesis is the prison sentence which is the most dominant criminal sanction. This thesis focuses primarily on the prisoners' rights such as the right to work and the right to health care, but the rights of prisoners cannot be exercised properly due to overcrowding, which is a major problem of the Croatian prison system. Although one of the most important principles of our legislation is the principle of classification, in practice, this principle is not implemented, so different groups of delinquents are mixed, leading to criminal infection. Various internal and international mechanisms have been supervising the protection of prisoners' rights, however, prisoners' rights continue to be violated and Croatia has been convicted several times before the European Court of Human Rights for violating Article 3 of the European Convention on Human Rights (prohibition of torture, inhuman and degrading treatment). The Croatian prison system faces a number of problems that make it difficult to resocialise prisoners, and in such conditions it is difficult to prepare prisoners for the world outside the prison’s walls. It is also very important to mention the European Committee for the Prevention of Torture, which has repeatedly warned about the problem of overcrowding in its reports, and alternatives such as community service, fine and suspended sentence are mentioned as one of the solutions. ,