In this study we present the outcome of a study carried out on 63 insulin-dependent diabetic patients from the Endocrinology Department of a hospital in Madrid. Our goal was to assess the relationship between psychosocial variables and treatment adherence and to obtain a discriminant function with which it was possible to classify the patients on the basis of assessed adherence level. Results show a positive relationship between self-reported adherence to therapy and metabolic control. We also found that physical exercise and relations with medical personnel were the main variables determining treatment adherence.