Objectives: To develop and psychometrically evaluate a domain-specific questionnaire to assess subtle but clinically relevant differences in treatment experiences and satisfaction over a wide range of currently available insulin therapy regimens. The study focussed on patients with type 2 diabetes mellitus and placed particular attention on the impact of different forms of insulin therapy on diabetes self-management. Methods: The development of the Insulin Treatment Experience Questionnaire (ITEQ) was conducted in three steps: (i) a qualitative phase to generate relevant items and identify relevant domains; (ii) a pilot study to reduce the number of generated items; and (iii) a validation study to assess major psychometric properties of the final ITEQ version. Results: The final version of the questionnaire comprised 28 items with the subscales ?leisure activities? (four items), ?psychological barriers? (two items), ?handling? (five items), ?diabetes control? (six items), ?dependence? (five items), ?weight control? (three items), ?sleep? (two items), and one further item assessing general treatment satisfaction. The subscales? internal consistencies (Cronbach?s alpha) ranged from 0.52 to 0.83. Motivated by the homogenous structure of inter-scale-correlations (range 0.10?0.46), a summary composite score was calculated (alpha = 0.86). Construct validity showed statistically significant correlations with other scales (ITEQ vs the Problem Areas in Diabetes [PAID] questionnaire total score -0.60, ITEQ vs the Diabetes Treatment Satisfaction Questionnaire [DTSQ] total score 0.52). Conclusion: The newly developed ITEQ displayed satisfactory to good psychometric properties, thereby allowing the assessment of everyday life experience and treatment satisfaction in patients with insulin-treated type 2 diabetes. Additional research is needed to assess test-retest reliability and sensitivity to change.