problem gamblers often exhibit additional, addictive behaviours in addition to gambling. rates of other disorders, including depression and substance use, are much higher in problem gamblers than in the general population. the present study examined data from all clients receiving treatment for addiction in thunder bay from 2003 till mid 2006. it was found that 73.9% of gambling clients had a comorbid substance addiction. a distinction was also found between two subgroups of problem gamblers - those who presented with gambling as their primary problem, and those who presented with another disorder as their primary problem and reported gambling to be a secondary problem. the demographic profiles of these two groups differed: clients with gambling as the primary problem were significantly more likely to be female, widows or widowers, employed or on retirement income, older, better educated and without any legal problems. the rate of substance comorbidity in the primary gamblers was only 20.6%, indicating that failure to differentiate primary from secondary gamblers results in an overestimate of substance comorbidity for those clients who have primarily a gambling problem.