AIMS. To compare and contrast gamblers with different forms of problematic gambling activities. DESIGN. Pathological gamblers completed the Addiction Severity Index (ASI) and gambling questionnaires when initiating out-patient treatment. PARTICIPANTS. Participants (n = 347) were categorized by their most problematic form of gambling activity: sports, horse/dog-races, cards, slots and scratch/lottery tickets. Differences in demographics, gambling variables, and ASI composite scores were compared across groups. FINDINGS. After controlling for demographic variables, the types of gamblers differed in severity of gambling, alcohol and psychiatric problems. Horse/dog-race gamblers were generally older, male and less educated; they began gambling regularly at a young age and spent relatively high amounts of money gambling. Sports gamblers were young males and had intermediary gambling problems; they had relatively high rates of current substance use but few psychiatric problems. Card players spent low to moderate amounts of time and money gambling, and they generally reported few alcohol problems and little psychiatric distress. Slot machine players were older and more likely to be female. Slot gamblers began gambling later in life, had high rates of bankruptcy and reported psychiatric difficulties. Scratch/lottery gamblers spent the least amount of money gambling, but they gambled the most frequently and had relatively severe alcohol and psychiatric symptoms. CONCLUSIONS. Gambling patterns and severity of psychosocial problems vary by form of problematic gambling, and these differences may influence treatment recommendations and outcomes.