The purpose of the presentation is to give an overview of my doctoral dissertation project, which focuses on morphosyntactic errors in Czech and Russian Learner Finnish. The first part of the presentation will focus on available corpora of Learner Finnish and on the International Corpus of Learner Finnish (ICLFI). The second part of the presentation will focus on the Czech and Russian subcorpora of the International Corpus of Learner Finnish. After introducing the subcorpora, I will turn to research questions related to morphosyntactic errors made by Czech L1 and Russian L1 learners of Finnish. Then, I will describe the error annotation system which was developed in order to identify morphosyntactic errors in the Russian L1 subcorpus (the Czech L1 subcorpus already contains error annotation). Finally, I will present the results of a pilot study of a subset of the Czech and Russian L1 subcorpora, to which the new error annotation system was applied.