BACKGROUND: Dietary Diversity Score (DDS), as a proxy for nutritional adequacy, can be used as a useful tool to assess diet quality, especially in children, due to its low cost and ease of use in comprehensive studies. This study aimed to develop a questionnaire to estimate dietary diversity and also assess the validity of DDS as an indicator of nutritional status among children aged 24 to 59 months in Iran. METHODS: In addition to the Dietary Diversity Questionnaire (DDQ), which was designed based on the Food and Agriculture Organization (FAO) protocols, two non-consecutive 24-hour dietary recalls were completed for 471 children aged 24-59 months, recruited using random cluster sampling. Nutrient Adequacy Ratio (NAR) for energy, protein, and micronutrients, and the Mean Nutrient Adequacy Ratio (MAR) were calculated. Serum retinol concentration was assayed using High Performance Liquid Chromatography (HPLC). Children's weights and heights were measured and Height for Age (HAZ), Weight for Age (WAZ), Weight for Height (WHZ), and BMI for Age (BAZ) Z-scores were calculated according to World Health Organization (WHO) criteria in 2006. Pearson correlation analysis was performed to analyze the correlation between DDS and NARs, MAR, anthropometric indicators, and serum retinol. RESULTS: The mean age of the children was 42.5 ± 0.47 months. The average DDS was 5.19 ± 0.06. DDS showed a positive association with the NAR of energy, protein, and all micronutrients (p <
0.05) except for vitamin K. There was a positive and significant correlation between DDS and MAR (r = 0.271
p <
0.001). In addition, DDS showed a direct, weaker but statistically significant, correlation with serum retinol concentration (r = 0.104
p = 0.026). No significant relationship was found between DDS and children's growth indicators. CONCLUSIONS: The designed DDQ can be a valuable tool for examining the adequacy of nutritional intake in Iranian children.