This article aims to present the significance of therapy in the Polish correctional system in positive social reintegration of persons executing the penalty of deprivation of liberty. The article is composed of four parts. The first part presents the grounds for utilizing therapy for inmates. The second part of the article indicates the aims of executing the penalty of deprivation of liberty by prisoners, including those convicts who suffer from health disorders. Characteristics of therapeutic system of sentence execution, with the emphasis on standards which are to be followed in correctional therapy, have been described in part three of the article. The last part includes information pertaining to the effectiveness of therapeutic treatment in persons executing isolation sanctions.