Aim of this study is to investigate the nutrition knowledge, dietary behaviors, and dietary habits by the gender in high school students in Chungnam province. Girls students had a higher score than boys students for nutritional knowledge, not in the significant difference. However, boys students had a higher score for dietary behaviors than girls students. Dietary habits showed a significant difference in the unbalanced food habit and eating speed by the gender, and the eating speed of boys students was faster than that of girls students. For boys students, the nutritional knowledge and dietary behaviors did not have the significant correlation. Otherwise, girls students had the positive correlation between the nutritional knowledge and dietary behaviors, and had the characteristics of behaviors that the higher the nutritional knowledge score, the better eating habit. In addition, the boys and girls students had the positive correlation between the score of nutritional knowledge and the frequency of breakfast, and the score of nutritional knowledge and the frequency/regularity of breakfast, respectively. Because some dietary habits/behaviors are related closely to their nutritional knowledge, the high school students need the systematic and steady nutritional education to apply their known nutritional knowledge to actual life.