Conditional relations in the Russian language are expressed by various means, including prepositional and case forms in a simple sentence. The article analyses non-derivative prepositions capable of expressing conditional semantics. In addition to the prepositions at, under, in, for which the conditional meaning is fixed in the language system, the authors examine the prepositions without, with, on, by, which also express the conditional meaning in speech. The material was the statements extracted from the National Corpus of the Russian Language and the Integrum database. The method of transformational analysis was used in the study of the material. The authors describe the factors that influence the lexical meaning of non-derivative prepositions and draw a conclusion about the functional-semantic features of syntaxemes with these prepositions.