Research Motivation: Despite improvement of the trends in levels and experiences of dental caries in developed countries, it remains prevalent and is increasing in some developing countries. In this study we assessed the relationship between dietary regimens and dental caries in 9-year-old students in Tehran, Iran. Research Design/Methodology: The sample was selected by using multi-stage sampling from all the public primary schools in Tehran. 560 students were assessed using WHO questionnaires and dental examinations according to WHO criteria by indices of dmft and DMFT. The frequency of nutritional snacks consumed was determined in the following week on each individual. The acquired data were described according to abundance charts and indices of means and standard deviations. A linear regression test also was used. Main findings and implications: The mean dmft and DMFT of the students were 3.93 and 0.79 respectively. The study showed that the use of snacks such as cream-filled biscuits (P=0.030), plain cakes (P=0.048), cookies (P=0.008), caramel cream (P=0.009), milk-based ice creams (P=0.017), hard candies (P=0.003), popcorn (P=0.013), cheesy snacks (P=0.000), and bananas (P=0.002) significantly increased dmft in the study group. Furthermore, the use of snacks such as pistachios (P=0.036), cookies (P=0.03), caramel cream (P=0.048) and sugar-based chewing gums (P=0.008) showed a consequential relationship with the increase in DMFT. According to the results, the variety of the consumed snacks was high among 9-year-old students. The dietary habits including Oranges, Pies and Caramel Cream affected the incidence of the dental caries in both deciduous and permanent teeth.