The subject of this work are special investigative techniques within the criminal procedure, which are regulated by the Criminal Procedure Act. This work starts with analysis of the criminal procedure in general and the basic concepts of criminal procedure, such as the reasonable doubt, the term of special investigative techniques and the practice that are currently facing courts in the Republic of Croatia. In the second part of this work is examined the subject of special investigative techniques, specifying the general and special conditions for the application of special investigative techniques and the content of special investigative techniques, where are exhaustively stated the types of actions, explaining the procedure of implementation and the conditions for their application. After that are comparatively shown the special actions in other European and American legal systems and their methods of work. In the following is illustrated the judicial practice of the European Court of Human Rights and Constitutional Court of the Republic of Croatia, with special attention paid to the supervision and technical monitoring of persons, premises and telecommunications, where was mentioned the violation of Article 6 and Article 8 of the European Convention of Human Rights, and how the European Court interpreted the various cases of European countries. In the judgements of the Constitutional Court will be talks about the consent of the provisions of the Criminal Procedure Act with the Constitution and how much invasive legal provisions related to the special investigative techniques affect the privacy of the people. In the end follows the comparison of the work and powers of police officers with the operatives of the security-intelligence community and the issues regarding to their discretionary powers.