This paper describes the results of a research project aiming to document the acquisition sequence of a set of L2 Polish morphosyntactic structures. In order to verify the hypothesis that acquisition sequences are largely independent of the learner’s L1, data were collected among two groups of learners, i.e. speakers of typologically and genetically distant languages relative to Polish, on the one hand, and speakers of East Slavic languages (Belarusian, Russian, Ukrainian), on the other hand, all of which are lexically and grammatically very close to the target language. Data were obtained through a survey and an Elicited Imitation Task.While Slavic learners systematically achieved higher performance than their non-Slavic counterparts, the acquisition sequences of the two groups proved to a large extent comparable. These results suggest an interaction between a general processing advantage deriving from a close relation between the L2 and one’s L1, on the one hand, and universal acquisition constraints, on the other hand.