International audience ; Objectives To investigate the reproducibility of the HELENA food frequency questionnaire (FFQ), developed as a basis for an online tailored intervention and to compare the FFQ with four computerized 24-hour recalls. Subjects/methods A convenience sample of 48 Belgian-Flemish adolescents completed four computerized 24-hour recalls, the FFQ and a retest one to two weeks later. Correlations, the Wilcoxons Signed Rank test and Bland and Altmans plots were used to compare intakes of 22 food groups, energy (kcal), fibre (g, g/1000 kcal), vitamin C (mg, mg/1000 kcal), calcium (mg, mg/1000 kcal), iron (mg, mg/1000 kcal) and fat (g, % from total energy). Results Reproducibility correlations were good (0.46-0.90). De-attenuated correlations between both methods were high (≥0.51) for all nutrients and nutrient densities, except for fibre (g), vitamin C (mg) and % energy from fat (respectively 0.23, 0.40 and 0.30). On a food group level correlations were significant (runadjusted>0.3) for most (17/22) food groups. No systematic differences were found between test and retest; comparison with the recalls resulted in a significantly higher intake of bread, breakfast cereals, other snacks, vegetables, potatoes, coffee & tea, alcoholic beverages, energy, and most nutrients. No significant difference was found for calcium whereas an underestimation was found for nutrient density of calcium and fat. Conclusions The overestimation in seven food groups, resulting in an overestimation of energy, fibre, iron and vitamin C and the underestimation of percentage energy from fat needs to be considered when the estimated intakes are used for tailored feedback.