Background and aims: Pathological gambling is a condition for which there is still no FDA-approved treatment although some medications seem to be effective at reducing its symptoms. In DSM-V, it is now classified as an addiction disorder. Data show that baseline comorbidities in patients with gambling and substance misuse behavior are frequent. These might include not only major syndromes but also subclinical ones. Bipolar spectrum conditions are often among these comorbidities. Lithium has been showed to be effective in PG subjects with bipolar spectrum comorbidity, and we present a case where assessment of temperament was helpful in treatment selection. Conclusions: This case illustrates the clinical benefits of how the assessment of temperament and comorbidities in pathological gambling patients may guide the clinician to a successful treatment choice. The case presented also corroborates previous evidence on the efficacy of lithium in patients with pathological gambling and comorbid bipolar spectrum conditions and euphoric temperament. Future clinical trials on pathological gambling pharmacotherapy should include temperament assessment to evaluate its influence on different outcomes.