OBJECTIVES: Weight management and exercise are key self-management treatments for patients with type 2 diabetes mellitus (T2DM).  This study examined the association between trying to lose weight or exercising regularly and health-related quality of life among individuals with and without T2DM. METHODS: Respondents to the US Study to Help Improve Early evaluation and management of risk factors Leading to Diabetes (SHIELD) baseline survey reported if they had tried to lose weight during the last 12 months and if they currently exercised regularly for >6 months.  Respondents also completed the SF-12 quality-of-life survey 1 year later.  The Physical Component Score (PCS) and Mental Component Score (MCS) of the SF-12 were computed, and differences between T2DM respondents (n = 2419) and respondents with no diabetes mellitus (n = 6750) were tested using t-tests.  Linear regression models adjusted for age, gender, race, education, household income, body mass index (BMI), and diabetes status. RESULTS: Among T2DM respondents, 71% reported trying to lose weight in the past 12 months and 20% reported exercising regularly for >6 months, compared with 64% of respondents without diabetes reporting trying to lose weight and 25% exercising regularly.  After adjusting for demographics, BMI and diabetes status, trying to lose weight was not associated with higher PCS scores (p = 0.87), but was independently associated with higher MCS scores (p = 0.01) in the subsequent year.  After adjustment, exercising regularly was significantly associated with higher subsequent PCS and MCS scores (p <0.001). CONCLUSIONS: Respondents with T2DM who reported exercising regularly had significantly better physical quality of life, compared with respondents without diabetes who exercised regularly.  Respondents with T2DM who reported trying to lose weight or exercising regularly for >6 months had better mental quality of life, compared with respondents without diabetes who tried to lose weight or exercised.