Predicting and providing an account for the difficulty of English relative clause comprehension for L2 learners has been attempted within frameworks such as noun phrase accessibility hierarchy (Keenan & Comrie, 1977), and filler-gap hypothesis (e.g. O`Grady, Lee & Choo, 2003). The current study probes whether the frameworks can effectively account for native Korean learners` errors and comprehension of English RCs. The result shows that multiple factors should be considered, rather than a single framework, in order to explain the difficulty of English relative clauses for Korean L2 learners. This research examined 25 intermediate Korean learners of English using a picture selection task. The result and error analysis suggest that several factors such as the number of intervening nodes demonstrated by the filler-gap hypothesis, canonical word order of English, length of relative clauses, and relative marker used in the relative clauses influence the English learners` comprehension. The findings may assist developing an efficient pedagogical tool for teaching English relative clauses.