Adult native speakers have a vast amount of knowledge (e.g., lexical, grammatical, pragmatic) of their first language, most of which is automatic, implicit, unverbalisable in nature. In contrast, L2 learners, as opposed to native speakers, rely more heavily on metalinguistic (Krashen, 1982), explicit, declarative (Ullman, 2004), less integrated (Jiang, 2007), less automatized (Segalowitz, 2003) knowledge and require more time, deliberate effort and conscious awareness to access and retrieve it. In my talk, I will report some results comparing the acquisition of L2 English article by L1 Spanish and L1 Russian speakers and discuss the role that the speaker’s L1 may play in the development of both explicit and implicit knowledge systems.