Children are frequent victims of concussive brain injury (CBI). But attempting to discuss pediatric CBI is something like painting a racehorse in full stride. Whatever one might infer from an exquisite study of 2-year-olds cannot be assumed to be applicable to 5- or 9- or 12- or 17-year-olds. The fantastically paced brain changes from birth to maturation at about age 25 mandate prudence. So do the weighty consequences of any conclusions. At this transitional point in the evolution of CBI knowledge, we know enough to be deeply concerned that some subset of children -- or type of injury, or age of exposure, or number of repetitions, or variant of post-injury management -- might shift the pathway of long-term outcome from relatively benign to devastatingly malignant. But we do not know enough to take well-informed action. The present chapter reviews what is known about differential vulnerability and long-term effects. The authors respectfully exhort society to consider how it might reduce the net loss of brain function and sum of human misery to which some children are doomed until neuroscience learns much more.