Objective: To assess the impact of comorbid heart disease, stroke and arthritis on health-related quality of life (HRQL) in people with diabetes in the general Canadian population. Methods: Data were collected as part of the 1996–1997 Canadian National Population Health Survey. HRQL was assessed using overall Health Utilities Index Mark 3 (HUI3) and single attribute utility scores. Respondents (N=66,093) were classified into 1 of 16 groups based on the presence or absence of diabetes, heart disease, stroke, and arthritis, in all possible combinations and HRQL scores were compared using analysis of covariance. Results: Overall HUI3 scores for respondents with diabetes alone (0.88, 95 CI: 0.87–0.89) were lower than controls (0.92 95 CI: 0.92–0.92, p0.001). Overall HUI3 scores for diabetes in combination withheart disease (0.77, 95 CI: 0.74–0.79), arthritis (0.78, 95 CI: 0.77–0.79) or stroke (0.79, 95 CI: 0.74–0.85) were considerably lower than diabetes alone. Triplets of comorbidities were associated with overall HRQL deficits of approximately 0.26–0.30, relative to controls. Conclusions: The illness burden experienced by individuals with diabetes is not only associated with diabetes itself, but largely with comorbid medical conditions.