Objectives. (1) To assess the current presence of ADHD symptoms among patients seeking treatment for gambling disorder; (2) to explore clinical and sociodemographic differences between patients who score high and low on the measure of ADHD symptoms; (3) to analyze whether the presence of ADHD symptoms is associated with more severe psychopathology and with specific personality traits; (4) to analyze the mediating role of ADHD symptoms in the relationship between novelty seeking and gambling severity.Method. A total of 354 consecutive patients were administered an extensive battery assessing gambling behavior, psychopathology, and personality traits.Results. Male and female gamblers did not differ significantly in their mean scores on the ADHD measure. However, younger participants aged 18–35 scored higher. Higher ADHD scores were also associated with greater severity of gambling disorder and more general psychopathology. Regarding personality traits, high persistence and self-directedness were negatively related to ADHD scores, while in women alone a positive correlation was found between ADHD scores and scores on harm avoidance and self-transcendence.Conclusion. The presence of ADHD symptoms in both male and female gambling disorder patients may act as an indicator of the severity of gambling, general psychopathology, and dysfunctional personality traits.