Background: There is relatively little research examining the relationship between Attention-Deficit/Hyperactivity Disorder (ADHD) and gambling addiction. This study seeks to explore for ADHD symptoms in adult gambling addiction patients and to evaluate their gambling-related cognitions. Materials and Methods: A cross-sectional survey was conducted at National Addictions Management Service, Institute of Mental Health, in Singapore. Patients presenting for gambling treatment were screened for ADHD symptoms and assessed for severity of gambling-related cognitions. The primary objective was to observe the rate of patients screening positive for ADHD. Results: 20% of the sample screened positive for ADHD. These individuals also had lower levels of gambling-related cognitions. No significant correlation was noted between ADHD symptoms and gambling-related cognition scores. Conclusions: Positive screening results for ADHD occurred frequently in our sample of Pathological Gambling (PG) and Problem Gambling patients and these affected individuals also exhibited lower levels of gambling-related cognitions. This finding may suggest that the gambling behavior in patients with ADHD-PG comorbidity is driven by impulsivity rather than gambling-related cognitions, which has implication on treatment considerations. Further research with a larger sample size is indicated.