This study examined whether vocabulary knowledge has meaningful effects on reading comprehension of Korean high school EFL learners and investigated which specific type of vocabulary knowledge, between vocabulary breadth and depth, plays a bigger role in reading comprehension when the learners’ English language proficiency is taken into account. The participants of this study were ninety eight high school EFL learners in Seoul, Korea, and they were tested on a series of measures tapping on their reading comprehension abilities and vocabulary knowledge in two different dimensions (vocabulary breadth and depth). Their listening comprehension abilities were also measured in order to control for the effects of general oral language comprehension abilities known to be the foremost contributor to reading comprehension and thus to enable focused analysis of the role of vocabulary knowledge. The study findings revealed that 1) vocabulary knowledge itself played a critical role in predicting reading comprehension abilities even after controlling for their listening comprehension abilities and that 2) compared to vocabulary breadth, vocabulary depth played a relatively more important role in predicting reading comprehension, regardless of the learners’ language proficiency. The findings provide important implications for vocabulary and reading comprehension instructions for Korean EFL students.

I. INTRODUCTION
II. LITERATURE REVIEW
    1. Vocabulary Knowledge and Reading Comprehension
    2. Vocabulary Breadth
    3. Vocabulary Depth
    4. Vocabulary Breadth vs. Depth
III. METHOD
    1. Participants
    2. Materials
    3. Data Analysis
IV. RESULT
V. DISCUSSION AND CONCLUSION
REFERENCES

• Yusun Kang(Department of English Language Education Korea University) corresponding author
• Hey Seung Kang(Department of English Language Education Korea University)
• Jieun Park(Department of English Language Education Korea University)