This study investigates the relation between syntactic complexity and register in Russian. Our corpus-based analysis shows a systematic correlation between registers or so-called spheres, defined by situational-functional parameters, and three measures of linguistic complexity, namely, frequency of clausal subordination, noun frequency and Mean Dependency Distance (MDD) (Liu, Journal of Cognitive Science 9:159–191, 2008). The analysis reveals that traditional assumptions about frequency of clausal subordination in particular functional spheres are not justified, and that frequency of clausal subordination and MDD display different register profiles. First, clausal subordination is most frequent in oral, specifically, oral public texts, in line with observations for English and contrary to traditional assumptions for Russian. In contrast, official-business, technical and educational-scientific texts contain relatively few subordinate clauses. Second, the frequency of clausal subordination across spheres forms a mirror image of noun frequency suggesting that the two act as variants of one variable in a variationist sense. Finally, MDD is highest in the official-business and lowest in the oral public sphere. This could be due to differences in mere sentence length rather than in syntactic complexity. Nevertheless, clausal subordination is obviously distributed very differently across spheres than MDD, the latter conforming more to traditional thought about complexity and register.