The main aim of my thesis is to investigate the monolingual learner’s dictionary in many respects: needs of the users who look for a certain piece of information in a monolingual dictionary, comparison of monolingual learner’s dictionaries with other types of dictionaries (bilingual and general monolingual), micro-structure, macro-structure, the usability of this type of dictionary for learners and then I am going to deal with the question whether it is worth teaching monolingual learner’s dictionary usage and how the teacher is advised to bring it into class. Last but not least I am going to report and evaluate the questionnaire that I had compiled and gave to about 30 students at the Kossuth Lajos Secondary School in Debrecen and to a group English major university students. But before doing that let me give you a brief history of the monolingual learner’s dictionary.