Sweetened beverage and fast-food intake have been identified as important targets for obesity prevention. However, there are few brief dietary assessment tools available to evaluate these behaviors among adolescents. The objective of this research was to examine reliability and validity of a 22-item dietary screener assessing adolescent consumption of specific energy-containing and non–energy-containing beverages (nine items) and fast food (13 items). The screener was administered to adolescents (ages 11 to 18 years) recruited from the Minneapolis/St Paul, MN, metro region. One sample of adolescents completed test–retest reliability of the screener (n=33, primarily white adolescents). Another adolescent sample completed the screener along with three 24-hour dietary recalls to assess criterion validity (n=59 white adolescents). Test–retest assessments were completed approximately 7 to 14 days apart, and agreement between the two administrations of the screener was substantial, with most items yielding Spearman correlations and κ statistics that were >0.60. When compared to the gold standard dietary recall data, findings indicate that the validity of the screener items assessing adolescents' intake of regular soda, sports drinks, milk, and water was fair. However, the differential assessment periods captured by the two methods (ie, 1 month for the screener vs 3 days for the recalls) posed challenges in analysis and made it impossible to assess the validity of some screener items. Overall while these screener items largely represent reliable measures with fair validity, our findings highlight the challenges inherent in the validation of brief dietary assessment tools.