BACKGROUND: This study aimed to assess children's diet quality in Crete and the potential role of several socio-demographic factors related to it. METHODS: Between October 2005 and March 2006, 481 primary school children were recruited from Crete. Dietary intake data was obtained using a combination of techniques comprising a 24 h recall and 3 food diaries. The Healthy Eating Index (HEI) was calculated summing the individual scores (0-10) assigned to 10 index components. RESULTS: The majority of participants (84.5%) had diet that 'needs improvement' (HEI score: 51-80). Twelve percent of participants had 'poor diet' and only 3.5% of schoolchildren had 'good diet' (HEI score >80). The overall mean of the HEI score was 60.5. The mean values of the HEI components score ranged between 2.8 (that is, the HEI component that measures vegetables intake) and 9.9 (that is, component that expresses the variety of consumed foods). Low mean values were found in the total fat and saturated fat components (3.7 and 3.4, respectively). Moreover, the HEI score was strongly associated with dietary macronutrients and micronutrients intake. CONCLUSION: On the basis of the HEI score, the vast majority of children were found to have a diet that 'needs improvement'. This indicates the increased necessity of drawing and implementing nutrition education programs targeting both children and their families and aiming to increase vegetables and fruits intake and reduce fat intake.