The article discusses the relationship between the concepts of purpose, function and tasks of criminal procedure. Criminal procedure is one of the instruments of power, serving the social need to protect the violated rights and legitimate interests of an individual and a citizen, the interests of the state and society. The author believes that the purpose of the criminal procedure should be regarded as protection of the rights and legitimate interests of individuals and legal entities, victims of crime, protection of the interests of the state and society, fair and impartial justice, prosecution of the perpetrators, and just sentencing for the guilty as well as judgment of nolle prosequi of the innocent ones and their rehabilitation. It is concluded that the function of the criminal procedure should be understood as an intrinsic property of the criminal justice system ensuring the implementation of the expected quality of the main activities carried out by participants of the proceeding in accordance with their role and purpose in the field of criminal justice. Discrimination between functions and tasks is based on role the entity activity is aimed at. The functions defining the type of activity and task solution in this case are closely connected. Therefore, one should speak of functional tasks in different forms of activity. However, the Criminal Procedure Act does not clearly define the functional tasks of bodies and officials engaged in the application of substantive and procedural law.