Introduction: Alcohol dependence (AD) is frequently associated with attention-deficit/hyperactivity disorder (ADHD) as well as with posttraumatic stress disorder (PTSD). Objective: Aim of this study was to investigate whether in patients with AD, ADHD is associated with an increased rate of exposure to potentially traumatic events (PTEs) and PTSD, with increased PTSD severity and higher impact on daily functioning. Methods: Patients with AD were thoroughly assessed for ADHD during long-term residential treatment. Participants also completed the Posttraumatic Diagnostic Scale (PDS). The PDS is a 49-item self-report instrument that assesses exposure to different PTEs, DSM-IV criteria for PTSD, severity of PTSD, and related functional impairment. Results: Of 341 patients with AD, 66 were diagnosed with ADHD (19%). ADHD was associated with a more frequent exposure to PTEs (88 vs. 65%, p < 0.001). In patients with PTEs (n = 237), odds for PTSD were higher in ADHD versus no-ADHD patients (OR 8.9, 95% CI 3.9–20.5). Furthermore, PTSD severity and functional impairment were increased in ADHD patients. Conclusions: ADHD in patients with AD is associated with a higher frequency of PTEs and PTSD with more severe and more impairing PTSD symptoms. In alcohol-dependent patients with ADHD, regular screening for PTSD should be considered.