The dissertation discusses the problem of lexical indicators of the hypothetical modality to be observed in Polish and Lithuanian. To begin with, the definition of the hypothetical modality along with its paraphrase has been formed. Furthermore, the gradational character of the category has been analyzed. There have been distinguished six groups of lexemes, which express particular degrees of the hypothetical modality - ranging from that expressing the trace of uncertainty (minimal degree of probability) to that expressing almost complete certainty (maximum degree of probability) . The resemblances and differences between the languages have been noticed. In the research area, the method of contemporary contrastive studies utilizing the interlanguage and the experimental Polish-Lithuanian corpus have been applied.