FinnWordNet is a wordnet for Finnish that complies with the format of the Princeton WordNet (PWN) (Fellbaum, 1998).It was built by translating the Princeton WordNet 3.0 synsets into Finnish by human translators.It is open source and contains 117000 synsets.The Finnish translations were inserted into the PWN structure resulting in a bilingual lexical database.In natural language processing (NLP), wordnets have been used for infusing computers with semantic knowledge assuming that humans already have a sufficient amount of this knowledge.In this paper we present a case study of using wordnets as an electronic dictionary.We tested whether native Finnish speakers benefit from using a wordnet while completing English sentence completion tasks.We found that using either an English wordnet or a bilingual English-Finnish wordnet significantly improves performance in the task.This should be taken into account when setting standards and comparing human and computer performance on these tasks.