BACKGROUND: Little is known about the impact of childhood trauma (CT) on the clinical profile of individuals with co-occurring substance use disorder (SUD) and post traumatic stress disorder (PTSD). AIMS: To compare the clinical characteristics of individuals with SUD+PTSD who have a history of CT with SUD+PTSD individuals who have experienced trauma during adulthood only. METHOD: Data were collected on 103 individuals as part of a randomised controlled trial examining the efficacy of an integrated psychosocial treatment for SUD+PTSD. Participants were recruited from substance use treatment services, community referrals and advertising. Data were collected on demographic characteristics, substance use and treatment histories, lifetime trauma exposure, and current physical and mental health functioning. RESULTS: The vast majority (77%) of the sample had experienced at least one trauma before the age of 16, with 55% of those endorsing childhood sexual abuse. As expected individuals with a CT history, as compared to without, evidenced significantly longer duration of PTSD. Those with a CT history also had more extensive lifetime trauma exposure, an earlier age of first intoxication, and reported more severe substance use (e.g., a greater number of drug classes used in their lifetime, higher severity of dependence scores and greater number of drug treatment episodes). CONCLUSION: Individuals with co-morbid SUD+PTSD who have experienced CT present with a more severe and chronic clinical profile in relation to a number of trauma and substance use characteristics, when compared to individuals with adulthood only trauma histories. It is therefore important for SUD+PTSD treatment planning that CT be carefully assessed.