We conducted cross sectional study in secondary school students in Hungary. The aim of study was to investigate the relationship of dietary habits and Body Mass Index (BMI). Our results showed that fast food consumption has a significant effect over BMI and its consumption cause an increase in BMI. Salty snacks consumption is inversely related to BMI. Our study showed that if a student is enrolled in high school he tends to have lower BMI value than the one who is studying in vocational school. Perception about body shape is significantly associated with BMI, the students who perceived their body shape is too fat they tended to have higher BMI. All other variables like eating breakfast, consumption of fruit, vegetables and sweets etc were found to have insignificant effect on BMI.