Other ; Background: Childhood trauma exposure (CTE) is frequently reported by those with substance use disorders (SUDs). SUDs also frequently co-occur with attention deficit hyperactivity disorder (ADHD). Objective: To investigate the role of childhood trauma exposure (CTE) in the presence and the persistence of ADHD in treatment seeking SUD patients. Method: Data was derived from the International ADHD in Substance Use Disorder Prevalence (IASP) study. A structured interview was administered to 1274 treatment-seeking SUD patients aged 18 to 65. Results: CTE was present in 53.5% of the patients and comorbid adult ADHD in 14.1%. CTE was significantly asso- ciated with ADHD: the prevalence of adult ADHD with and without CTE was 19.4% and 8.5% (OR adjusted for age, gender, main substance of abuse, BPD, and ASPD 1.91 [95% CI 1.29–2.81]). CTE was not associated with the sever- ity of adult ADHD or with the persistence of childhood ADHD into adulthood. Conclusions: CTE is common in SUD patients and associated with adult ADHD but not with the persistence of childhood ADHD into adulthood. These findings suggest that the increased rate of adult ADHD in SUD patients with CTE is not the consequence of a negative effect of CTE on the persistence of childhood ADHD into adulthood, but a direct expression of the high rate of childhood ADHD in SUD patients with CTE.