BACKGROUND: The aims of this study were (1) to demonstrate the reliability and validity of the Impact of Weight on Activities of Daily Living Questionnaire (IWADL), a measure of ability to perform daily physical activities, in individuals with type 2 diabetes who are moderately obese and (2) to characterize those individuals with low self-reported ability. METHODS: Data from a web-based survey of individuals with type 2 diabetes and body mass index (BMI) of 30-40?k/mg(2) were used to calculate Cronbach's ? and demonstrate both IWADL factorial and construct validity. These data were entered into a multivariable multinomial logistic regression model with survey variables (demographics, health status, weight- and diabetes-related) as the independent variables and three IWADL scoring groups (Low, Medium, and High) as the dependent variables. RESULTS: Study participants were 349 individuals with type 2 diabetes (mean age?=?59 years, 44% male, 91% white, mean BMI?=?35?k/mg(2)). Factor analysis indicated a one-factor solution for a seven-item IWADL with Cronbach's ??=?0.94. Significant (P?<?0.05) relationships were identified between IWADL and variables previously shown to be related to level of physical activity. Ten variables remained independently (P?<?0.05) related to IWADL scores, including age, gender, health status, current exercise, using exercise programs or hypnosis as a step to lose weight, and self-reported weight history. CONCLUSIONS: The IWADL is a reliable and valid measure of the ability of individuals with type 2 diabetes and moderate obesity to perform daily physical activities. This ability may be an important patient-reported end point to include in clinical trials of antihyperglycemic medications that produce weight loss.