Objective: To analyze adolescents' opinion on healthy and unhealthy foods. We conducted a cross-sectional study involving adolescents from public and private schools. Methods: The sample was stratified in three stages: school, class and student, resulting in 1507 surveyed adolescents. The adolescents answered questions on healthy and unhealthy foods. Results: A total of 995 adolescents answered the questionnaire and were considered for analysis. By and large, adolescents agreed on the benefits of fruits for health. There was disagreement between responses of public versus private school students with regard to the health risks of processed salty snacks and French fries; private school students, as well as females, agreed that soft drinks contribute to weight gain and obesity, while those belonging to the public schools disagreed; adolescents from private schools, female and adolescents aged 15 to 17 years disagreed that red and fatty meats protect against heart diseases. Conclusion: Adolescents from private versus public schools, females compared to males, and who were older demonstrated a better understanding of the negative health effects of soft drinks and meat consumption