PURPOSE: To examine the relationships of exposure to school-based tobacco prevention programs and perceived usefulness of such programs to smoking susceptibility. METHODS: An ethnically representative sample of 6929 Grade 10 students participated in a cross-sectional survey of tobacco-related activities and behaviors. Perceived usefulness of prevention programs was investigated according to two dimensions: perceived helpfulness of information received at school with regard to making decisions about tobacco use and perceived availability of social resources that might help students cope with tobacco-related issues. RESULTS: The extent of exposure to school prevention programs and both dimensions of perceived usefulness of these programs were inversely associated with susceptibility to smoking. In addition, perceived information helpfulness mediated the effect of program exposure on susceptibility status, whereas perceived availability of social resources moderated that effect. The study also presented evidence suggesting ethnic/cultural variability in the status of susceptibility to smoking at this age. CONCLUSIONS: The study indicates a need to examine the perceptions of students receiving school prevention programs. Perceived usefulness of school prevention programs may be used to identify youth at high risk for smoking susceptibility. Future studies, however, should investigate other dimensions of perceived usefulness as well as intrapersonal, interpersonal, and environmental correlates of this construct.