|Abstract:||L2 English learners are known to use some language cues (e.g. context, phonology, or affixes) to infer the meanings of unknown words. Some prior studies (Bellomo, 2009; Kieffer & Lesaux, 2012; Koda, 2000; Ramirez et al., 2011) have found that learners’ L1 may influence the performance; however, their participants’ L1 and proficiency levels were not carefully controlled, and they mainly used qualitative or classroom-based methods. Therefore, this study compared the word learning ability between high proficiency L2 English learners of L1-Korean (a language with rich derivational morphology) and L1-Chinese (a language with only a small amount of derivational morphology) by using the reaction-time technique. English pseudo-words were used in this study, and learners had to infer the meaning of those words by using the morphological cues (i.e. re-, mis-, -ness, -able, un- and -er) and/or the contextual cues provided. Learners’ accuracy and reaction time were recorded; based on previous research it was predicted that L1-Korean L2-English learners would be faster than L1-Chinese L2-English learners in identifying morphological cues in words because of the existence of rich derivational morphology in Korean. However, the results of this study indicated that Korean participants did not have an advantage over Chinese participants in word learning using morphological cues.