Background: Lower energy density diets tend to cost more, but data using different ways to calculate the dietary energy density, is scarce.Objectives: To estimate the dietary energy density, and to assess how it is associated with the diet costin children.Methods: Data were obtained from a community-based survey from public elementary schools in Portugal.Dietary intake of 464 children (6-12 years) was assessed by a 24 h recall in 2007/2008. Dietary energy density (kcal/g) was calculated as following: (1) with food and all beverages (ED1), (2) with food and caloric beverages (ED2), and (3) only with food (ED3). Energy-adjusted diet cost (D /1000 kcal) was calculated based on the collection of food prices from a national leader supermarket. Anthropometric measures were taken and socio-demographic data were obtained from parents. Logistic regression was used to estimate the association between diet cost and energy density.Results: For boys, the energy-adjusted diet cost of the highest third of energy density was lower, between 81% in the ED3 (p for trend lt;0.001) and 87% in the ED1 (p for trend lt;0.001), compared to the lowest third. Girls showed similar, but weaker associations.Conclusions: Higher dietary energy density was associated with lower dietary cost among children.