The article explores main approaches to the study of mental lexicon, beginning from the first definitions of this phenomenon to the most modern ideas on this issue. As the result of this theoretical review, we can conclude that the mental lexicon stores not just word forms but concepts and contains different kind of information apart from the conceptual one, such as semantic, grammatical, syntactic associative types of information as well as additional extralinguistic information. Besides, the article examines some of the most popular models of the organisation of mental lexicon in our mind.