This study was aimed to examine nutrition knowledge, dietary attitudes, and eating habits of elementary school students and to examine if their characteristics differ by gender. Subjects were 5th and 6th graders of an elementary school (n = 317) in Seoul, and the survey was done during July 2007. Mean height, weight, BMI of subjects was 148.1 cm. 41.7 kg, 19.0, and 14.3% of subjects were categorized as the overweight/obese group. Anthropometric data were not significantly different by gender. Mean score of nutrition knowledge was 14.9 out of 20 showing moderate knowledge levels, and girls scored higher on nutrition knowledge than boys (p < 0.05). Subjects showed knowledge deficit in areas such as nutrients, food groups and specific weight control information. The percentages of correct answers regarding meals for brain function were significantly higher in girls than in boys (p < 0.05). They got nutrition information mainly from mass media and family/relatives. The mean score of dietary attitudes was 41.2 (possible score: 10-50) indicating somewhat positive attitudes, and the score of eating behaviors was 34.8 (possible score: 15-45). Subjects showed problems in eating habits such as having unbalanced diets and snack foods. 82.6% of subjects had unbalanced meals, and these percentages were higher in girls (87.2%) than in boys (78.1%, p < 0.05). Vegetables and fish/shellfish were the most disliked foods. Specific eating behaviors, such as eating slowly, eating grains and having processed foods less frequently, were better in girls than in boys (p < 0.05). Results also showed that majority of subjects need to improve specific behaviors including having diverse foods, eating meals slowly, having meals at regular times, having adequate foods in each food groups, and eating sweets or salty foods less frequently. Only 52.7% of subjects perceived their body images as normal, and 56.4% had experience of weight control. Reasons for weight control were different by gender (p < 0.05). Based on these findings, nutrition education for school children should focus on modifying eating habits or eating behaviors, by suggesting practically applicable methods and providing nutrition information that is interesting and suitable to school-aged children.