ABSTRACT The aim: The article aims to deepen the scientific discussion on ensuring the right to psychiatric assistance in places of deprivation of liberty. Materials and methods: In preparing the article, the following were examined: the provisions of international legal instruments regulating adequate treatment of persons suffering from mental disorders; relevant legal positions of the European Court of Human Rights in this regard; and scholarly research within the outlined vector of scientific inquiry. The methodological basis of the study consists of dialectical, comparative-legal, systemic-structural, analytical, synthetic, and comprehensive methods. Conclusions: The current case law of the European Court of Human Rights indicates that subparagraph “e” of paragraph 1 of Article 5 of the Convention for the Protection of Human Rights and Fundamental Freedoms (lawful detention of persons of unsound mind) serves two protective functions: a social one (ensuring the protection of society) and a therapeutic one (providing the person with adequate treatment while in detention). The comprehensive concept of “adequate treatment of a person suffering from mental disorders” includes the following components: a) an individual treatment plan; b) an appropriate institution; c) the language in which the treatment is provided. Adequate treatment is an integral part of the concept of an “appropriate institution”. The right to adequate treatment becomes illusory if there is a language barrier between the medical staff and the patient suffering from mental disorders. KEY WORDS: adequate treatment, compulsory medical measures, criminal process, ECHR practice, mental disorder.