This study was carried out to examine dietary habits, food frequency and dietary attitudes by gender and nutrition knowledge level in upper-grade school children. Subjects were 223 boys and 208 girls attending 13 elementary schools (5 th and 6 th graders). A self-administered questionnaire was developed to assess nutrition knowledge, dietary habits, food frequency, and dietary attitudes. Nutrition knowledge score assessed by 19 questions was significantly higher in girls than in boys. There were significant differences between boys and girls in several items in dietary habits such as enough breakfast time, dinner regularity, number of side dishes, eating speed, type of snack after dinner, and degree of saltiness of dishes. Girls consumed staple foods such as rice, noodles or bread more frequently, and consumed less frequently ramyun, fried foods, fast foods, and Chinese foods than boys. In addition, girls had more positive dietary attitudes in trying to reduce fast foods, Chinese foods, ramyun and fried foods. Also children in the high or moderate nutrition knowledge level groups had better dietary habits in frequency of meals, frequency of breakfast, enough breakfast time, dinner regularity, activity during the meal, number of side dishes, eating speed, type of snack after dinner, and better food choices by eating staple foods and vegetable side dishes, meats and beans more frequently, and fried foods, doughnuts/cakes, Chinese foods less frequently, and had better dietary attitudes in breakfast, vegetables and fruit intake than children in the low nutrition knowledge level group. Our results showed that dietary habits, food frequency and dietary attitudes were different by gender and nutrition knowledge level. These results suggest that in developing nutrition education program for elementary school children, the differences between gender and nutrition knowledge level should be considered. Nutrition education in elementary schools may change dietary habits and dietary attitudes through increasing nutrition knowledge.