A survey was conducted to determine the relationship between BMI and the dining out behaviors of 316 university students in Seoul area for May and September, 2006. The subjects included 114 males and 202 females. General characteristics and BMI determined that of the students 56 (17.7%) were underweight, 222 (70.3%)were normal, 23 (7.3%) were overweight, and 15 (4.7%) were obese. There were differences in BMI according to age, sex, and major. Students majoring in natural science and engineering were 58.3% and 51% normal weight, respectively, and the next most common weight class was overweight. The non smoking group showed had primarily normal weight subjects followed by underweight-subjects, but the smoking group had primarily normal weight subjects followed by overweight subjects (P<0.001). The frequency of dining out for breakfast significantly correlated with BMI (P<0.05). The group that frequently dined out for breakfast were primarily of normal weight followed by overweight subjects, but the group that rarely dined out for breakfast were primarily of normal weight followed by underweight subjects(21.4%). Groups whose criteria for selecting dining out meals were flavor and price showed a higher percentage of underweight subjects than other groups. The group whose motivations for choosing dining out meals were convenience and habit showed a higher percentage underweight subjects than other motivations. The group that selected the Western food menu for dining out showed a higher percentage of underweight subjects than other food menu groups. And, the groups that selected Japanese and Korean food were primarily of normal weight followed by underweight subjects, but the result was not significant.