Constructions тот, кто vs. тот, который in Modern Russian and Russian as L2

The functioning of constructions тот, кто и тот, который in modern Russian has specific features which are important for teaching Russian as a foreign language, since students often make mistakes while using them. The purpose of the work is to identify the principles of the usage of the constructions in modern Russian and by Russian-language learners by describing the distribution capabilities of constructions in standard Russian, by determining the degree of influence of grammatical features on the choice of relative pronoun, and by analyzing the texts of Russian-language learners. The qualitative and quantitative method of language data analysis of NKRYa, RLC, experimental materials are presented in this work. The results of the analysis confirm that the choice of the relative pronoun depends on the number and gender of the antecedent. Students also tend to make mistakes while using plural number of the predicate in the relative clause.