A comparison of a parent-completed Willett food-frequency questionnaire (FFQ) and a self-completed Youth/Adolescent Questionnaire (YAQ) has not yet been conducted.

In the Diabetes Autoimmunity Study in the Young (DAISY), parents report their child's diet on the FFQ annually from birth until age 10 years, when the child begins to report their own diet using the YAQ.

To determine the comparability of these collection methods, 89 children aged 10–17 years and their parents completed the YAQ and FFQ, respectively, for the child's previous year's diet.

We compared reported intakes for energy, the macronutrients and a variety of micronutrients of interest to the DAISY study.

Bland–Altman plots of energy-adjusted differences between questionnaire responses against their means suggested that the two collection methods gave similar results. The average Spearman correlation coefficient of all energy-adjusted nutrient intakes was 0.50, and did not differ significantly by gender (males, r = 0.48; females, r = 0.46) or age (10–11 years, r = 0.49; 12–17 years, r = 0.51). While correlated, the nutrient values from the FFQ were higher than the nutrient values from the YAQ.

While reported nutrient intakes are correlated, an indicator variable defining which survey method a nutrient was collected with should be included in any longitudinal data analyses examining nutrient intakes collected with the YAQ and the FFQ as independent predictors of a disease outcome.