This article is devoted to the certain aspects of protection of liberty of thought, conscience and religion in the meaning of Art. 9 of the Convention for the Protection of Human Rights and Fundamental Freedoms. We have studied the complexity of the key concepts interpretation, the essence of which is guaranteed by the Convention, due to the lack of extensive practice of the European Commission on Human Rights and the Human Rights Court. It is noted that for a long time in a significant number of complaints the Convention body has come to the conclusion that the issues raised in the complaints, might be considered through the prism or Art. 10, as they concerned freedom of expression, or fell within the limits of Art. 11 of the Convention, which guarantees freedom of assembly and association. At the same time, the values protected by Art. 9 are related to those ones, which are provided in Art. 8 and demand the respect for privacy. It is also closely linked to the right of parents to provide such education and training as it is consistent with their religious and ideological beliefs, as guaranteed by Art. 2 of the First Protocol to the Convention.This article illustrates the fact that the conventional understanding of these complex, deep and multifaceted concepts at the present stage is formed with the development of the case law of the European Human Rights Court, which in its activities is guided by the principle of effective and dynamic interpretation of conventions and other related principles, which ensures the protective mechanism effectiveness. As the time is extended, the Court case-law has developed an approach that allows to assess the views that the petitioners plan to benefit from the protection of the Convention for the Protection of Human Rights and Fundamental Freedoms. Such views in the meaning of Art. 9 must, first of all, be to some extent "convincing, serious, holistic and meaningful" and, secondly, be "compatible with human dignity".Taking into consideration the compiled content of the right guaranteed by Art. 9, viz. that it contains two aspects such as forum internum (internal) and forum externum (external), the article notes that regulation can be involved only in the case of forum externum. As long as liberty of thought, conscience and religion remains within a human being, this right is considered to be absolute. The state has a negative obligation not to interfere in such a right.In the framework of this article, the author considers it appropriate to state the position of the European Union on the attitude and ways to effectively address these issues. As the subject of international law and one of the most influential international organizations based on the values of human dignity, freedom, equality and respect for human rights (Art. 2 of the Treaty on European Union), the EU advocates for their real protection, which requires the development of specific legal instruments.Therefore, both the EU internal and international activities are based on the principles that underlie its creation. It is the foreign policy aspect of the EU human rights activities that is the subject of our article that is reflected in the “European Union Guiding Principles on the Promotion and Protection of Religious Freedom or Belief”.The article draws a number of conclusions. First of all, the right of liberty of thought, conscience and religion is one of the key principle of a democratic society and the value in European cultural and historical heritage. The issue of violation of the right to freedom of religion or belief is interrelated with freedom of expression, freedom of assembly and association. The issues of combating various forms of discrimination are not set aside. Additionally, the right, guaranteed by Art. 9, is a fundamental right and one of the democratic society foundations and the value in the law of the European Union. Moreover, the EU identifies problematic issues in the field of protection of liberty of conscience and religion as those ones that require particular attention, and the EU makes efforts to address them not only within its borders, but as well as in the foreign policy relations and initiatives