The relation between dietary behavior and fast food consumption was investigated among 117 male and 164 female students at a high school in Seoul. The main reason for eating fast foods was convenience. In addition, they used fast food chain stores as a get together place with friends. They enjoyed taste of fast foods as well as the atmosphere of stores but they regarded fast foods somewhat expensive for high school students. Among them, 30.1% of the female students had irregular meals and they ate more irregularly than males. More students took too much or too little amount(45.3% of male, 52.5% of female students) than those who took adequate amount. They skipped breakfast the most frequently because they are in a hurry. Most students took snacks once a day and they considered taste of snacks was more important than nutrition or price. They consumed less calorie, calcium, iron, and riboflavin than RDA. Mean caloric intakes of males and females were 79.0% and 97.1% of RDA, respectively. Mean calcium and iron intakes were less than 70% of RDA. Among many factors that may influence nutrient intake, anthropometric indices turned out to be the most influential. Body weight showed significantly positive correlation with caloric, protein, thiamin, and ascorbic acid intakes in male students where both height and weight showed positive relation with calorie, protein, and iron intakes in females. Therefore, this study suggested that fast food stores should make efforts to provide more foods and beverages which are supplemented with calcium and iron. Also, better nutrition education programs should be established to improve high school students dietary habit to complement these nutrients.