Defence personnel have reported returning from deployment with physical and/or psychiatric symptoms. Of particular concern is the ‘signature injury’ for the recent wars in Iraq and Afghanistan; that being mild traumatic brain injury (mTBI) and how this may relate to the onset or maintenance of posttraumatic stress symptoms (PTSS). At present, it is unclear if standard treatments for PTSS are suitable for those with mTBI. Preliminary searches have revealed that there has been limited neuroimaging research reporting the impact of mTBI on PTSS. It is also of interest as to how mTBI may relate to the development or maintenance of substance misuse problems. Whilst the focus in this review is the impact of mTBI on PTSS, attention will also be paid to those that also review substance misuse due to the frequent comorbid presentation.