It has been acknowledged that the null subject of a converbial clause in Russian is canonically controlled by the Nominative subject of a main clause (that is, Nominative subject control). Non-Nominative control has been considered to be ungrammatical. On the basis of two experiments (an acceptability judgement task and speeded grammaticality judgement task), the paper shows that non-Nominative control with mental converbs is evaluated lower than grammatically correct, but higher than grammatically incorrect, sentences. Moreover, according to the data from the RNC, the frequency of non-Nominative control has been increased in more recent written texts (those written approximately after the 1950s). Furthermore, the paper reveals a new effect of the linear position of a converbial clause relative to a main clause (preposition vs. postposition). Preposed converbial clauses are judged to be more acceptable than postposed converbial clauses. In corpus texts that have been written more recently, there has also been a tendency for non-Nominative control to occur in sentences with preposed converbial clauses. Last but not least, the paper demonstrates that sentences with a 1SG pronoun are more acceptable than sentences without a 1SG pronoun.