The study on phraseology is wide and complex, since it examines different aspects of an entire linguistic branch. The current article takes into consideration the typology proposed by the Italian linguist Federica Casadei, which will serve as a basis for the authors’ categorization of specific Russian expressions. The purpose of this paper is to illustrate the full and partial correspondence of Italian and Russian phraseological units through a new schematization, and, at the same time, to propose a new categorization of the phraseological units applied to Russian expressions. Italian and Russian theories on phraseology are examined and compared. Italian theory is more focused on the classification of the phraseological units: idioms, sayings, transparent locutions, opaque locutions and higher lexical units. Russian studies are more oriented to cognitive aspects related to the metaphorization of phraseological units. However, linguists agree that stability and reproducibility are the two main criteria that combine all phraseological units. The main issue when translating from one language into another is that of conveying the source meaning through processes of paraphrase. The result is that some Russian denominations of specific entities can be classified as monomorphemes and some do not constitute part of non-autonomous group as they do in Italian. On the basis of the differences among categories, a hypothesis about the categorization of some Russian phraseological units is proposed. Furthermore, we underline the importance of metaphorization as a key element for understanding phraseological units. Through metaphors, native speakers can express figurative meanings and innate mental representations.