Various types of cognitive and behavioral impairments may occur after brain injury. Among the clinical specialties involved in these conditions, psychiatrists should take the initiative, especially in the management of aberrant social behaviors or psychiatric symptoms as long-term sequelae of brain injury. Some of the aberrant social behaviors might be understood as psychological reactions to physical impairment or social difficulties. Others might be better understood as direct consequences of brain injury. Apathy, disinhibition, and executive dysfunction are the three major domains of aberrant social behaviors after injury of the prefrontal cortex and its associated subcortical structures. In the case of traumatic brain injury, there are concerns both about over-diagnosis and under-diagnosis, especially when dual-diagnosis with post-traumatic stress disorder, or the diagnosis of “post-concussive syndromes”are considered. In such cases, in addition to detailed history-taking and psychiatric evaluation, neuroradiological data in the in the acute stage of brain injury are valuable.