Aim: To examine cortical activation during a memory task in children with and without post-concussion symptoms (PCS) following concussion. Methods: A case-controlled study within the PlayGame Trial (www.playgametrial.ca). Children (aged 8-18 years) with PCS at 1-month post-injury were eligible. The fMRI task was a working memory task. Pre-processing and single-subject analysis were performed in FSL. Group activation and inter-group difference maps were extracted. Results: 11 symptomatic, 12 asymptomatic, and 11 controls without concussion participated. Groups were similar in age (14.9, 14.0, and 13.8yrs; p=0.46), sex (p=0.984) and time post-injury (symptomatic: 37d; asymptomatic 35d; p=0.573). Compared with controls, symptomatic children demonstrated greater activation especially in the bilateral orbito-frontal cortex and cerebellum. A similar, less pronounced pattern was observed in asymptomatic subjects. Conclusions: Similar to adult studies, increased network activation may represent decreased “efficiency” and explain the cognitive fatigue in PCS. Further, children who are “asymptomatic” may not yet be fully recovered.