The purpose of this study was to distinguish which food is fast foods and to define the characteristics of fast foods. The 14 kind of foods(hamburger, pizza, fried chicken, raymyeon, hotdog, doughnut, fried fish cake, jajangmyeon udong, ice cream, dukbokki, spaghetti, sandwich, gimbab, and salad) and 5 characteristics of fast foods(takeout, franchise, fast serving, unhealthy, and cheap price foods) were selected based on the dictionary and previous research papers about fast foods for this study. A total of 306 male and female high school student in Daejeon area were participated. The data were gathered by questionnaire and analyzed by SPSS/WIN 18.0 program. The participants evaluated the fast foods as delicious and convenient foods but non-nutritious, i.e. high fat but vitamin deficient foods. Among the 14 foods examined, hamburger, pizza, and fried chicken were the foods which more than 90% of the participants acknowledged to fast foods. Dukbokki, spaghetti, sandwich, gimbab, and salad were the foods which less than 50% of the participant acknowledged to fast foods. Among the 5 characteristics of fast food examined, unhealthy foods showed the highest sensitivity, specificity, predictive value, and odds ratio(0.803, 0.712, 0.597, and 2.79, respectively), and cheap price showed the lowest values of those(0.565, 0.335, 0.242, and 0.85, respectively) for acknowledging foods to fast foods. As conclusion, hamburger, pizza, and fried chicken were the representative foods of fast foods. Fast foods are generally considered as fast served cheap price foods, but the participants did not think the fast foods as fast and cheap foods. The most distinguished characteristics of fast foods in the students' minds was unhealthy foods.