This paper considers the dictionary as a foreign language learning and teaching aid. I try to demonstrate how dictionaries can help learners of a foreign language, how they can be aids for teachers and as a background to all these I deal with the effort lexicographers should do. After this introductory part, in Chapter 2, I set my work into a context with presenting lexicography and dictionaries in general. The main part of my thesis is Chapter 3, which deals with learners’ dictionaries. Following a brief history of these special types of dictionaries I will write about the role of and debates around dictionaries in teaching. Then a section comes about what the users of dictionaries expect from their dictionaries. The next part describes what the users can actually get from these wordbooks considering all of the major areas of language: pronunciation; grammatical, pragmatic and semantic information as well as any other information these special dictionaries can offer for learners. The Fifth Chapter presents the latest inventions of our electronic world, i.e. the electronic dictionaries and their advantages and disadvantages over their paper counterparts. The last section before the conclusion is an empirical analysis. I try to show how these theoretical issues in the first part are put into practice: I compare a general monolingual dictionary, a monolingual learner’s dictionary and a bilingual dictionary to show which and in what respect offer more to learners.