The paper deals with the topic of human rights of prisoners in penal institutions, the importance of their respect and the ways of their violation. The first part of the work analyzes the rights of prisoners under the Law on Execution of Prison Sentences. As part of these rights, the paper will provide insights into practice examples in Croatia as well as in some European countries. Furthermore, it will show how the rights of prisoners are violated and what forms of supervision exist on the system of execution of imprisonment sentences. The second part of the paper deals with the social reintegration of prisoners into the community and the problems that prisoners face in that period of life. Emphasis is put on the importance of preparing the inmates to leave during the execution of prison sentences. A key role in adapting the inmates to freedom of life also has a probe system. Considering this, the paper will analyze the probation system in the Republic of Croatia and the probation system in some European countries. It will offer examples of good practices of co-operation with other organizations, and will therefore suggest the improvement of our probation system. At the end of the work, the role of social work in the protection of prisoners' human rights, in the process of adaptation to life in the penitentiary institution and later, after returning to the community and involving the person in everyday life activities, will be considered.