BACKGROUND: The current study aimed to assess the diet quality of Greek preschoolers and the potential role of several sociodemographic factors related to it. METHODS: A representative sample of 2,287 Greek children aged 2 to 5 years (from the Growth, Exercise, and Nutrition Epidemiological Study In preSchoolers) was used in this work. Dietary intake data was obtained using a combination of techniques comprising weighed food records, 24-hour recalls, and food diaries. A Healthy Eating Index (HEI) score was calculated summing the individual scores (0 to 10) assigned to each one of 10 index components. RESULTS: Eighty percent of participants had an HEI score <50 (ie, "poor" diet), 0.4% had an HEI score >80 (ie, "good" diet), and the overall mean HEI score was 59. HEI scores were significantly higher among boys, children aged 4 to 5 years, children participating in moderate to vigorous physical activities for more than 3 hours per week, children living in rural or small towns, and those whose mothers were employed and had higher educational status (>12 years). HEI score was also found to be strongly associated with several macronutrient and micronutrient intakes. CONCLUSIONS: Based on HEI scores, the vast majority of Greek preschoolers was found to have a poor diet. Moreover, low HEI scores were associated with low levels of physical activity, low vegetable intake, high saturated fat intake, lower maternal educational level, and unemployment status.