It is a fact that vocabulary has become the neglected area of language study. One main reason of this article is the trial to move the study of idioms firmly out of the domain of the phrase and the sentence into a consideration of the function of idioms in contexts of communication. This enables an exploration of the roles and functions of idioms in texts and discourses, both spoken and written, understanding the role of idiomatic expressions in the construction of interpersonal meanings, in the formation of coherent text, and in the creation of the stylistic effect. The lexical antonymy and the phraseological antonymy are particular cases of the lexical and of the phraseological meanings that share similitudes and differences. The same thing applies to the lexical and phraseological antonyms in the English and Romanian languages. This article focuses on the structure of phraseological units in the Romanian and English languages via a contrastive study. The author looks into the phraseological antonyms, by studying the lexical nature of their components.