Contemporary literature does not take a clear position on the issue of determining civil and criminal liability of persons diagnosed with pathological gambling, and all the more so in case of possible comorbidity of or interference with other mental disorders. Diagnostic difficulties are demonstrated by a clinical picture of a patient with problem gambling who underwent forensic and psychiatric assessments to evaluate the process of making informed (and independent) decisions in view of numerous concluded civil law (mainly financial) agreements. The patient had been examined 5 times by expert psychiatrists who, in 4 opinions, diagnosed her with bipolar affective disorder, including 1 diagnosis of rapid cycling of episodes. Based on the current state of scientific knowledge about the relationship between problem gambling and mood disorders, bipolar affective disorder was not confirmed. Diagnostic difficulties, resulting both from diagnostic haziness and unreliable information obtained during patient interview, that emerged in the course of case study point to the need for multi-dimensional clinical diagnosis of persons with suspected mood disorders and behavioral addictions.