Korean has visually salient syllable units that are often mapped onto either prefixes or suffixes in derived words. In addition, prefixed and suffixed words may be processed differently given a left-to-right parsing procedure and the need to resolve morphemic ambiguity in prefixes in Korean. To test this hypothesis, four experiments using the masked priming lexical decision paradigm were conducted. Results showed that suffixed primes facilitated responses to their stem targets regardless of the lexicality or interpretability of the primes. In contrast, prefixed primes had a significant effect only when they were real words, and not when they were either interpretable or noninterpretable prefixed pseudowords. These results suggest that there may be two different processing mechanisms for derived words in Korean. One is prelexical morphological decomposition for suffixed words, and the other is the supralexical analysis for prefixed words where decomposition occurs only after the whole word has been accessed.