This textbook is in the form of a series of lectures on the special course “Fundamentals of the qualification of crimes”, covering the least developed and relevant issues of law enforcement. The content of the work is structured based on the state and correlation of levels of qualification errors made in legislation, investigative and judicial practice, as well as in doctrinal interpretations of the Criminal Code of the Russian Federation. For each group of analyzed problems, recommendations are offered on the correct, from the author’s point of view, classification of crimes. For future and current lawyers, as well as readers who are concerned about the situation with the rule of law in modern Russia.