The work on this monograph devoted to the interpretation of the European Convention on Human Rights grew out of the conviction that there is still a need for in-depth theoretical investigations in this field. The aim of this study is not to discuss in a comprehensive and detailed way all the rules of interpretation employed by ECHR, but rather to look from the theoretical perspective at what are, in the author's opinion, the main problems associated with this interpretation. Therefore, particular chapters are devoted to such issues as: the application by the Strasburg Court of the methods of interpretation stipulated in the VCLT, since the Convention is an international agreement; the principles of interpretation of the ECHR which should play a leading role in the process of interpretation; the main methods or doctrines of interpretation the method of proportionality, dynamic interpretation (the living instrument), autonomous interpretation, and the doctrine of the margin of appreciation. Separate chapters deal with the problem of the order in which the different methods should be applied, the determinants of the Court's interpretation of the ECHR, and the question of the constitutional character attributed to the Convention and to the Court. In this study, the author puts forward the research hypothesis that there is a significant correlation between, on the one hand, the way the ECtHR interprets the Convention and, on the other, the level of legitimacy enjoyed by this judicial body and the level of success achieved in the process of its constitutionalization.