In this paper I develop a mechanism of interpreting Korean “wh-phrases”. The phrases have various readings depending on where they occur and they could be ambiguous even in the same structure. Yet their readings are subject to certain restrictions. I assume that the “wh-phrases” behave like variables and that there are three quantifiers to bind the phrases; $COMP_{wh},;COMP_{conc}$ and derivational $exists$-quantifier. Based on the assumptions I suggest derivational quantification, which consists of three conditions. 1) A quantifier can bind only when it merges into the derivation; 2) $exists$-quantifier accompanies 〔-OP〕 complementizer but its activation is optional; 3) an instance of quantification makes the clause opaque to other instances of quantification. Scrambling data support derivational approach and across-the-board interpretation motivates the opacity condition. The opacity condition accounts for ATB- interpretations of reflexive pronouns. It can also explain the island effect of wh-islands without adopting covert wh-movement in Korean.