The paper deals with one of the significant aspect of fairness in criminal cases, the concept of "equality of arms". The considerations focus initially on the analysis of the scope and meaning of the notion of "equality of arms" in the case-law of the European Commission and the European Court of Human Rights under Article 6 of the European Convention on Human Rights. The author reviewed the Strasbourg case-law on the concept of "equality of arms" in the context of three different but connected procedural topics: equality between the parties in the institutional framework of criminal proceedings, "equality of arms" principle in the evidentiary proceedings in general and "equality of arms" under Article 6 of the Convention in the jurisprudence concerning criminal trials involving anonymous witnesses. Subsequent chapters of the paper survey the application of this notion to different models of criminal procedure, namely to the common law system (of which England is a good example) and to the model of procedure adopted in the countries of Continental Europe (e.g. Germany and Poland). The analysis does not provide for a comprehensive treatment of all national regulations concerning the issue of equality between the parties in a criminal process. Its objective is rather to emphasise the general approach to the principle of "equality of arms" in different models of criminal justice. The final chapter of the paper focuses on the issue of the possible convergence of different models of criminal procedure adopted in Europe with the one model based on the standards and principles emerged form the jurisprudence of the organs of the Convention.