The Institute of Slavic Studies of the Polish Academy of Sciences, as part of the CLARIN-PL consortium, is engaged in the creation of multilingual corpora of Slavic and Baltic languages. Some of the planned corpora have already been made available in the dSpace CLARIN-PL repository and in the KonText online browser. One of these corpora is the Polish–Lithuanian corpus, which in this article serves to illustrate the possibilities of applying CLARIN-PL corpora in research into the Polish language. The Lithuanian language has an archaic structure in comparison with Polish. Lexemes are characterised by a clearer structure. There are regular connections between grammatical form and meaning, with a small number of exceptions. These features of Lithuanian ensure that the projection of strongly formalised meanings onto Polish-language resources is a straightforward operation, leading to a significant narrowing of Polish-language resources, which can be analysed in the context of unequivocal interpretations based on Lithuanian meanings.