The paper considers constructions «sensation predicative + infinitive» and « interpretation predicative + infinitive». The infinitives of the movement, position and some others are typical for sensation predicative: Kholodno stoyat` / ekhat` ‘It`s cold to stand / to drive’; Temno idti / chitat` ‘It`s dark to go / to read’. Such an infinitive occupies an intermediate position between a valency and an adjunct. The infinitives in interpretation constructions expresses the valency of predicative: Nevezhlivo sidet` v prisutstvii damy ‘It is impolite to sit in the presence of a lady’. Such a predicative has a higher syntactic status than adjective or adverb, that are the original representation for interpretive vocabulary.