Economic security of Republic of Moldova is largely linked to the application of preventive measures against tax crimes. Tax crimes are the object of activity of law enforcement bodies and represent very complicated manifestation as deviation from the taxation is basically made by numerous hidden and refined me including specially organized financial, economic and criminal structures. Quite often criminal processes embrace the whole branches of economy, representing direct threat of economic security to the state. In the last years fluctuation of the criminogenic environment in an economic field, penetration of criminal structures into new market institutes and mechanisms has been noticed, which, undoubtedly, assumes fluctuations of methods and ways of struggle against crimes of an economic trend with the purposes of ensuring of economic security. The analysis of structure and methods of committing economic and tax crimes and offences is of major significance. It allows revealing regional, branch and problem priorities in the process of the activity of law enforcement bodies. Analysis of violations of the tax legislation and methods of taxation evasion reveals most often applied unfair methods and circuits and allows specifying disadvantages of the operating tax legislation.