This study investigated the predictors of posttraumatic stress disorder (PTSD) in children following a diagnosis of traumatic injury. Children (N=76) aged between 7 and 13 who were admitted to hospital following injury were assessed within a month of trauma for acute stress disorder (ASD), negative appraisals, as well as parental stress reactions. Children (N=62) were re-assessed 6-months later for PTSD and negative appraisals. The majority of the variance of chronic posttraumatic stress was accounted for by negative appraisals about future harm. This study supports cognitive models of PTSD, and suggests that younger children who exaggerate their vulnerability after trauma exposure are high risk for PTSD after trauma.