Childhood brain tumor survivors are at increased risk for neurocognitive impairments, including working memory (WM) problems. WM is typically assessed using performance measures. Little is known about the value of parent ratings for identifying WM difficulties, the relationship between rater and performance measures, or predictors of parent-reported WM problems in this population. Accordingly, the current study examined the utility of parent report in detecting WM difficulties among childhood brain tumor survivors treated with conformal radiation therapy (n = 50) relative to siblings (n = 40) and solid tumor survivors not receiving central nervous system-directed therapy (n = 40). Parents completed the Behavior Rating Inventory of Executive Function (BRIEF). Participants were administered WM measures (digit span, self-ordered search tasks). Findings revealed parents rated brain tumor survivors as having significantly more WM problems (p < .01) compared to controls. However, the BRIEF-WM scale demonstrated poor sensitivity and specificity for detecting performance-based problems. Significant, albeit modest, correlations were found between the BRIEF-WM scale and performance measures (r = -.24-.22; p < .05) for the combined group. Age at testing, socioeconomic status, and IQ were significant predictors of parent reported WM problems. Rater and performance measures offer complimentary yet different information in assessing WM, which reiterates the importance of using both within the context of clinical assessment.