Background: Substance use disorders present a tremendous challenge within contemporary healthcare systems. Specifically, in the domain of opioid use disorders (OUDs), several foundational elements are crucial for the efficacious management of afflicted individuals. Regrettably, the premature discontinuation of inpatient opioid withdrawal treatment is a prevalent phenomenon. This study aims to elucidate the prevalence of the premature termination of inpatient opioid withdrawal treatment among patients with comorbid ADHD. Methods: We conducted a comprehensive assessment of all participants currently undergoing inpatient opioid withdrawal treatment. Our assessment protocol included the administration of the ADHD Self-Report Scale (ADHD-SR) and the Wender Utah Rating Scale (WURS-k). Additionally, participants who met the thresholds on one or both questionnaires underwent further evaluation using the Diagnostic Interview for ADHD in Adults (DIVA-2.0). Results: The prevalence of individuals diagnosed with ADHD within the studied cohort was determined to be 29.3%. Among the subset of participants identified as ADHD-positive, a notable 54.5% prematurely ceased therapy. In contrast, among those identified as ADHD-negative, the premature discontinuation rate was substantially lower at 28.3%. Conclusions: In summary, the impact of ADHD as a comorbid condition on the efficacy of inpatient opioid withdrawal treatment has been underscored. By identifying comorbid ADHD early in the treatment process, tailored therapeutic approaches may help to maximize the effectiveness of interventions and may improve patient outcomes. This underscores the importance of proactive screening for ADHD as a psychiatric comorbidity in optimizing the management of individuals undergoing inpatient opioid withdrawal treatment.