OBJECTIVE: To determine whether age differences exist with respect to neuropsychological and electrophysiological functioning following a sport concussion. DESIGN: Cross-sectional study. PARTICIPANTS: Ninety-six athletes (9-12 years, n = 32; 13-16 years, n = 34; adults, n = 30), half of whom had a sport concussion. INTERVENTION: Cognitive functioning was assessed using standardized neuropsychological tests and event-related potentials elicited by a visual 3-stimulus oddball paradigm. The PCSS was used to assess symptoms experienced at the time of injury. MAIN OUTCOME MEASUREMENTS: Neuropsychological assessment with an adaptation of the battery used by the National Hockey League. Latencies and amplitudes of the P3a and P3b were analysed in terms of group (concussed vs. control) and age. RESULTS: All concussed athletes had significantly lower amplitude for the P3b component compared to their non-injured teammates (p > 0.05). Adolescents also showed persistent deficits in working memory (p > 0.05). CONCLUSIONS: These data suggest persistent neurophysiological deficits that are present at least 6 months following a concussion. Moreover, adolescents are more sensitive to the consequences of concussions than are children or adults.