Children and adolescents with maltreatment-related posttraumatic stress disorder (PTSD) exhibit smaller intracranial tissue volume than controls. Linear relationships have also been observed between intracranial tissue volume and the age of maltreatment onset. The authors explored associations among adult PTSD, early trauma, and cerebral volumes in 99 combat veterans. A bone-based estimate of cranial volume was developed to adjust for variation in body size. Posttraumatic stress disorder was not associated with smaller cerebral tissue volume, but rather with smaller cerebrospinal fluid (CSF) and cranial volumes. These findings co-occurred with expected effects of alcoholism and aging on cerebral tissue and CSF volumes. The results point to early developmental divergences between groups with and without PTSD following adult trauma.