The paper considers lexical reduplications in Russian in the perspective of general syntax. The goal is to define and fully characterize special Russian surface-syntactic relations [SSyntRels], that is, the reduplicative SSyntRels, which appear exclusively in syntactic idioms formed by lexical reduplications. The syntactic operation REDUPL is defined, and several reduplicative SSyntRels are introduced. A deductive calculus thereof is proposed, based on three parameters concerning the correlations between the reduplicate and the reduplicand: the reduplicate is anteposed/postposed (with respect to the reduplicand); is in contact/is not in contact (with the reduplicand); represents an exact/inexact copy (of the reduplicand); eight reduplicative SSynt-Rels are theoretically possible. The notion of syntactic idiom (a non-compositional multilexemic expression having a non-segmental signifier) is formulated and illustrated: e.g., the sentence Mne Y prazdnik X ne v prazdnik Lʹ(X) lit. ‘To me the feast is not into a feast’ = ‘I cannot enjoy the feast’, which implements the syntactic idiom [X to.Y] ˹be not into Lʹ(X)˺ ‘X cannot be enjoyed by Y’. Six reduplicative SSyntRels of Russian and one of English are described. These SSyntRels are conceived as a fragment of a general inventory of SSyntRels in the world languages.