This study investigated the relationship between L2 learning and learners' cognitive variables, and figured its research trend and issues. Studies on language aptitude, working memory, and executive functioning were selected and reviewed. Most studies revealed the advantages of high language aptitude, high working memory, and high executive functioning on L2 learning (explicit or implicit), feedback intake (explicit feedback or recast), and language skill (reading, speaking, listening, pronunciation, vocabulary, grammar, and speech act) accomplishment and so on. However, this study claimed that more study results should be accumulated to provide solid research results of cognitive variables on detailed areas of L2 learning, and proposed future research issues. Especially in research of L2 Korean learners, cognitive factors have been rarely studied and restricted in their topic. More research should be implemented to draw their own results on L2 Korean learners that shed light on understanding L2 Korean learners and help find better teaching and learning methodology. (Kyung Hee University)