This scientific article is dedicated to explanation of the concepts existed in the modern penal science of the Republic of Moldova in the matter of extra-activity of the criminal law. The object of scientific discussions takes part from the most neglected topics of the Substantive Criminal Law. During this research the author tries to define the following concepts: „extra-activity of the criminal law”, „ultra-activity of the criminal law”, „retroactivity of the criminal law” and „the lenient criminal law”, being proved that sometimes the conflicts in time exists between criminal laws.