Objective. To quantify the variation in emergency department (ED) wait times by patient race/ethnicity and payment source, and to divide the overall association into between- and within-hospital components. Data Source. 2005 and 2006 National Hospital Ambulatory Medical Care Surveys. Study Design. Linear regression was used to analyze the independent associations between race/ethnicity, payment source, and ED wait times in a pooled cross-sectional design. A hybrid fixed effects specification was used to measure the between- and within-hospital components. Data Extraction Methods. Data were limited to children under 16 years presenting at EDs. Principal Results. Unadjusted and adjusted ED wait times were significantly longer for non-Hispanic black and Hispanic children than for non-Hispanic white children. Children in EDs with higher shares of non-Hispanic black and Hispanic children waited longer. Moreover, Hispanic children waited 10.4 percent longer than non-Hispanic white children when treated at the same hospital. ED wait times for children did not vary significantly by payment source. Conclusions. There are sizable racial/ethnic differences in children's ED wait times that can be attributed to both the racial/ethnic mix of children in EDs and to differential treatment by race/ethnicity inside the ED.