The purpose of this study was to investigate the relationship among nutritional status, serum lipids and leptin of 134 elementary school students with different obesity index residing in Kyunggi-do, Korea. Subjects were assigned to under weight, normal weight or over weight group according to the their obesity index. Their nutritional status, serum lipid and leptin levels were evaluated based on 24-hr dietary recalls, anthropometric measurements and blood analysis. The mean weight, height and obesity index of total subjects was 150.8cm, 45.6kg and 5.4%. The mean % of body fat was higher while LBM and TBW (total body water) were lower in over weight subjects than those of other two groups. Total food, plant protein, carbohydrate, and vitamin C intakes of underweight male students were lower than those of overweight male students. The consumption of total fat was the highest in the female normal weight subjects and the lowest in female overweight subjects. Male students consumed more plant protein and vitamin C than female students. The mean daily intake of vitamin B$_2$, calcium and zinc of all subjects did not meet the Korean RDA. Also, iron intake of female students was lower than the Korean RDA. The mean level of serum leptin was the highest in male and female overweight subjects (p＜0.001). The HDL-cholesterol level was the highest in the underweight group of male subjects (p＜0.05) and in the normal weight group of female subjects (p＜0.001) The serum level of leptin and atherogenic index (AI) of females were higher than those of males. Serum leptin of total subjects had significantly positive correlation with obesity index, weight, SBP, body fat, cholesterol intake, serum triglyceride, and AI. However, serum leptin was negatively correlated with LBM, TBW, intake of plant protein, vitamin B$_1$, vitamin C and serum HDL-cholesterol. Obesity index was also positively correlated with weight, SBP, body fat, serum triglyceride and AI. To summarize the results, the vitamin B$_2$, calcium, zinc, iron and fiber intakes should be supplied to elementary school students, especially those who were overweight. The average serum leptin level of students showed remarkably positive correlation with obesity index, body fat, serum lipids and AI. Also, it was suggested that the serum leptin might be related to the dietary factors like cholesterol, plant protein, vitamin B$_1$ and vitamin C of elementary school students.