The aim of the present study was to analyze comorbid Axis I-disorders in a sample of individuals with at-risk, problem, and pathological gambling. A number of 164 adult gamblers derived from a random sample of 15,023 individuals were compared with a general population sample. The lifetime prevalence of any psychiatric disorder was 93.6% among pathological (five-10 criteria), 83.5% among problem (three or four criteria), and 81.0% among at-risk gamblers (one or two criteria). Substance use disorders were the most common comorbid disorders in gamblers. Logistic regression analyses revealed elevated odds ratios for having a comorbid disorder in at-risk (Conditional Odds Ratio (COR) 3.5, Confidence Interval (CI) 2.6-4.6), problem (COR 4.9, CI 3.3-7.3), and pathological gamblers (COR 4.6, CI 3.0-6.9) compared to the general population. No significant differences were found between at-risk and problem gamblers or problem and pathological gamblers. Compared to at-risk gamblers, pathological gamblers showed elevated rates of comorbid substance use disorders. The data suggest a linear association between gambling disorder severity and comorbid Axis I-disorders. In conclusion, comorbid disorders are very prevalent in individuals with gambling problems. Even at-risk gamblers with one or two DSM-IV criteria show high rates of Axis I-disorders. Therefore, this group should be included in further studies on problematic gambling.