OBJECTIVE: To assess obesity's impact on the health-related quality of life (HRQL) of diabetes patients in the U.S. METHODS: Adults (age >= 18) with diabetes (ICD9CM = 250) in the 2000 and 2002 Medical Expenditure Panel Survey (MEPS) were classified as underweight (BMI<18), normal weight (BMI:18-24.9), overweight (BMI:25-29.9), or obese (BMI: >=30). Underweight individuals were excluded from the study sample. HRQL was assessed using SF-12 physical, SF-12 mental and EQ-5D index scores. These scores were used to compare obese vs. normal weight and overweight vs. normal weight populations. Stratification matching methods were employed to control for demographic differences between comparison groups (e.g. age, sex, race, and geographic location). Differences in HRQL scores are reported using both absolute difference and effect sizes (ES). Individual MEPS weights were used to achieve U.S. nationally representative estimates. RESULTS: A total of 2,777 adults with diabetes are included in the study, of which 497 are of normal weight, 903 are overweight, and 1,377 are obese. SF-12 physical and EQ-5D index scores for the obese sample were 4.35 and 0.06 lower (4.35% and 6.27%; ES = 0.35 and 0.19, respectively) than the normal weight sample (p<.05). All differences reported control for age, sex, race, and geographic location. There were no statistically significant differences in the SF-12 mental scores between the obese and normal weight samples. Similarly, SF-12 mental, SF-12 physical and EQ-5D index scores were statistically no different between the overweight and the normal weight populations. CONCLUSIONS: Obesity is associated with a statistically significant reduction in physical HRQL and overall health utility among diabetic patients in the United States but does not seem to affect their mental health. On the other hand, overweight leaves physical, mental and overall health utility scores unchanged relative to a normal weight population.