Patients suffered from DM, face many difficulties in compliance to medical instructions, because the DM type II may be asymptomatic at the beginning and that is the reason that recommended dietary and lifestyle changes may seem unnecessary. The aim of the study was to develop a specific instrument measuring compliance to treatment in patient with DM II and test the validity and reliability of the instrument in Greek people. Method and material: This instrument was created using 38 questions from existing questionnaires. The questionnaires used were: Summary of Diabetes Self-Care Activities, 9-item Patient Health Questionnaire, 12-item Short Form Health Survey and Diabetes Self-care Behaviours and Barriers instrument. The translation process from English into Greek was undertaken following the guidelines provided by the International Committee of this instrument. Several issues related to the best possible translation and validation of the various dimensions and levels of the instrument were taken into account. Then the instrument was tested to a representative sample of 120 individuals. Results: Using the scale reliability of the Flesch-Kincaid, the reliability of the questionnaire was 6.7. The average time for completing the questionnaire was eight minutes (SD ± 4.2 minutes). The instrument presents construct validity, discriminant ability, reliability and sensitivity to change. Conclusions: The present instrument requires considerable time to complete it. Therefore it is a reliable and valid instrument which can be used effectively in compliance of therapy measurement in Greek population.