This paper is addressed the problem of parametric variation in Russian grammar, with focus on copular constructions with agreeing and nonagreeing adjectival predicates. Basing on Russian National Corpus, I reconstruct two dialects of Russian morphosyntax. They differ regarding the assignment of the predicative instrumental case, raising conditions and the distribution of agreeing vs non-agreeing predicates after быть 'be', стать 'become' and казаться 'seem'. Russian-A only licenses predicative instrumental on adjectives after SEEM (казалось странным, что P) and non-agreeing predicatives after non-zero forms of BE or BECOME (было странно, что P). Russian-B allows non-agreeing forms after SEEM (казалось странно, что P) and forms of the predicative instrumental case after non-zero forms of BE and BECOME (было странным, что P). I argue that the differences between Russian-A and Russian-B must explained in terms of parametric settings and claim that Russian predicatives lack forms of the predicative instrumental. The assignment of the predicative instrumental to adjectival heads can be explained as subject control in all dialects, but only Russian-B allows raising of sententional arguments to the position of the matrix subject.