The purpose of this study was to investigate nutritional knowledge, practice of eating behavior guidelines, and problematic dietary habits in working high school students in comparison with non-working high school students. A survey questionnaire was formulated to obtain information on demographic variables, body size, part-time jobs, nutritional knowledge, practice of eating behavior guidelines, and dietary habits. The developed questionnaire was given out to 515 students attending a vocational high school in Yongin, Gyeonggi-Do. Those who had been working 5 hours or more per day for at least a month at the time of survey administration were defined as working students for this study. Proportions of working students were similar between male and female students (i.e. 49.5% for male, 50.5% for female). No significant difference was found in scores of nutritional knowledge between working ($8.43{pm}2.29$) and non-working students ($8.60{pm}2.19$). However, some dietary habits were found to be dependent on working status. While approximately 43% of non-working students reported skipping a meal, about 57% of working students did so (p<0.01). The proportion of students with any drinking experience was significantly higher among working students (92%) compared to non-working students (80%) (p<0.001). Working students were found to drink alcoholic beverages more often than non-working students (p<0.001). The mean score of practice of eating behavior guidelines was lower in working students than non-working students. The magnitude of this difference was modest ($51.33{pm}0.63$ in working students, $53.40{pm}0.51$ in non-working students), but reached statistical significance (p<0.01). Based on the findings from this study, it is suggested that specific behavior-oriented messages to improve certain problematic dietary habits need to be directed toward working high school students.