The purpose of this study was to determine factors affecting intention to participate in school breakfast programs of middle and high school students in Seoul using the Theory of Planned Behavior. Out of 2,280 questionnaires distributed to the middle and high school students, 2,060 were returned (90.4% response rate) and 1,799 were analyzed (78.9% analysis rate). To determine factors affecting intention to participate in school breakfast programs, logistic regression analyses were conducted for middle and high school students, respectively. For logistic regression, data of 1,217 out of 1,799 students (637 middle and 580 high school students) were used after excluding 582 students which had an answer 'Not sure' to the question about intention to participate in school breakfast programs. In case of middle school students, male than female students (OR = 1.504), the students who skipped all breakfast (OR = 1.851), who ate breakfast 1~2 times (OR = 3.474) or 3~4 times (OR = 1.950) than those who ate breakfast everyday during weekdays of the previous week were more likely to participate in school breakfast programs. In case of high school students, male than female (OR = 1.967), the students who skipped all breakfast (OR = 4.187), the students who ate breakfast 1~2 times (OR = 3.024) or 3~4 times (OR = 2.095) than those who ate breakfast everyday during weekdays of the previous week were more likely to participate in school breakfast programs. In addition, both possibility of middle and high school students' participation in school breakfast programs increased as the satisfaction with school lunch service (OR = 1.704, 1.653) increased. Middle school students who perceived their household income level 'low or middle low' (OR = 1.999) than those who perceived their household income level 'middle' and the students who had more positive 'attitude' (OR = 1.311) toward eating breakfast were more likely to participate in school breakfast programs. However, high school students who had higher 'perceived difficulty in access to breakfast' (OR = 1.370) were more likely to participate in school breakfast programs. The results of this study could be useful data to plan and develop school breakfast programs in Korea.