This study is to investigate the concerns about obesity and diet behaviors among 565 middle and high school students in Ulsan. The results indicated that high school students rather than middle school students and girls rather than boys had higher concerns about obesity and diet behaviors. For the socio-economic variables, being female, a high school student, and a group with the least monthly allowance was higher concern about obesity and diet; and household income, educational level and occupation of the fathers also had significant impacts on the student concerns about obesity and diet behaviors. The variables of height, weight, PIBW (Percentage of Ideal Body Weight), and BMI (Body Mass Index) had significant impacts on the concerns about obesity and diet behaviors. Especially, students with normal weight had the highest concerns about obesity and diet, while obese students had the lowest concerns. (J Community Nutrition 7(4): $184∼192$, 2005)