The present study aims to explore the relationships between the variables -- experience abroad, self-efficacy, and self-perceived proficiency -- and the self-concept in the L2 Motivational System and identify which of these variables contribute more to its explanation. Research data on 197 Korean university students majoring in English related studies were collected and analyzed using simple and hierarchical multiple regressions. This study re-confirms ideal L2 self as being more influential on motivated learning behavior than ought-to L2 self, which is consistent with many previous studies. It was also found that experience abroad is statistically related to ideal L2 self, but not to ought-to L2 self, which means, as experience abroad increases, ideal L2 self is likely to be enhanced. The results also identified the crucial role of self-efficacy in the formation of ideal L2 self while taking experience abroad into account. Additionally, the students' ideal L2 self was found to be more readily explained by their proficiency in communicative skills than that of academic skills.