This article examines the differences in effectiveness of 3 types of dictionaries— monolingual, bilingual, and “bilingualised” in the comprehension and production of new words by EFL learners. The participants in the research were 123 high school and university learners. The test consisted of 15 low-frequency words. Five were given with their entries from a monolingual learner's dictionary, 5 with their translations from a bilingual dictionary, and 5 with the entry from a bilingualised (or semibilingual) dictionary. The study tested participants on the comprehension of the target words and on their ability to use these words in their own sentences. The results of the experiment suggest that different dictionaries may be suitable for users with different abilities in dictionary use.