In this paper we report a factor analytic study on the ATT39, a measure of psychological adjustment to diabetes. The ATT39 was developed in response to the need for more specific measurement tools for the assessment of psychosocial issues in diabetes. The factor analyses in this study were conducted separately for insulin-dependent and non-insulin dependent patient groups to acknowledge the known clinical differences between these two subclasses of diabetes. The results showed a core of 19 items in a single subscale to be common to both IDD (Insulin-Dependent Diabetes) and NIDD (Non Insulin-Dependent Diabetes) patient groups based on rigorous factor analytic criteria involving the use of a factor matching technique (FACTOREP) and replication samples. Coefficient alpha values were in the range of 0.82 to 0.84, showing it to have acceptable internal reliability. Future research on the measure should focus on its clinical-usefulness to detect change in patient psychological functioning and to predict diabetes self-care behaviours and metabolic control.