The purpose of the study was to develop an instrument for measuring treatment compliance among people with type 2 diabetes and to test the validity and reliability of the Greek version of this questionnaire. The study survey was created by incorporating items from other questionnaires. The Flesch-Kincaid readability level of the instrument was 6.7. The average time required for completion was 8 minutes (standard deviation±4.2 minutes). The instrument showed sufficient validity, discriminant ability, reliability and sensitivity to change. The new questionnaire is easy to understand but requires considerable time to complete. It can be used to reliably measure treatment compliance among Greek people with type 2 diabetes.