The knowledge related with lexical items can be realized as including relations of meaning a cross words. Words that share a similarity of meaning are called to be synonymous, and words that share a contrary of meaning are called to be antonymous. Both of them are universal linguistic phenomenon that exist in terms of linguistic system of every language. The present study aims at finding out areas of difficulty that Iraqi EFL learners encounter in the use of synonymy and antonymy, both on the recognition and production levels. Also tries to detect the main reasons behind such difficulties. A diagnostic test of two parts, namely, recognition and production, is designed. The test is built to include two linguistic phenomenon which are: synonymy and antonymy. A random sample of one (100) third year College students of two Colleges of Education, in University of Baghdad and University of Diyala, (50) students each. Data analyzed were based on Cruse’s taxonomy (1986). The study has come up with the following conclusions: in spite of being students at an advanced level in learning English, they used a general lexical item, instead of their other synonyms and antonyms which imply a narrower sense of meaning. And although Iraqi EFL learners learn a number of synonym words and antonym words during their academic years of studying English, still they cannot utilize them correctly in context. Keywords: antonyms, production, recognition, synonyms