User comments are one of the common online resources that reflect users' evaluative opinions about multimedia contents. The words used in user comments provide many clues about the users and about what they like or dislike. In this paper, we propose a novel query expansion method that utilizes user comments in order to consider user's different preferences in finding movies. We propose a personalized search system, called MovieMine, built upon this proposed method to provide personalized search results by expanding queries on the basis of earlier comments left by the user. Using an actual movie review dataset obtained from a large movie portal, we show that our system produces a significant performance improvement compared to the baseline condition. We expect our approach to be readily applicable to personalized searching of multimedia contents.(1)