OBJECTIVE: For patients with type-1 diabetes, having a preferred insulin delivery system may lead to better compliance and better clinical and patient-reported outcomes. The purpose of this study was to assess the reliability and validity of the Insulin Delivery System Questionnaire (IDSQ), an instrument developed to measure overall insulin satisfaction and preference for an insulin delivery system. METHODS: The IDSQ was administered to 137 patients with type-1 diabetes at screening, baseline, crossover, and endpoint of a randomized, noninferiority, crossover trial designed to compare the glycemic control of injectable vs. inhaled insulin. Psychometric analyses included internal consistency (Cronbach's alpha), factorial validity (principal component analysis with Promax rotation), discriminant validity (ANCOVA model with baseline score and other covariates), and responsiveness (t-tests). RESULTS: Exploratory factor analysis indicated that there were three factors accounting for 73% of the variance. All items loaded above > 0.50 on either Factor one, lifestyle impact; Factor two, ease of dosing; or Factor three, satisfaction/preference with the exception of the “easy to control my blood sugar” (BG) item. Cronbach's alpha coefficients calculated for the factors were 0.93, 0.86, and 0.86, respectively. Each of the three factors and the BG item discriminated between those patients who preferred inhaled insulin and those who preferred injectable insulin (all p<0.001). Factors one and three and the BG item demonstrated the ability to detect change from baseline (injectable treatment) to following treatment with inhaled insulin (all p<0.001). Factor analysis and interscale correlations indicated that the 16 items could be summed to a total IDSQ score. Cronbach's alpha for the total score was 0.93. CONCLUSION: The IDSQ is a reliable and valid instrument to assess insulin delivery system satisfaction in patients with type-1 diabetes.