BACKGROUND ----- Research on the effects of treating sub-threshold depression in persons with diabetes is scarce in spite of the findings indicating that this condition is highly prevalent in the diabetic population and may increase the risk of developing a subsequent major depression. This study was aimed at exploring the effects of a psycho-educational intervention on depression- and diabetes-related outcomes in patients with mild to moderate depressive symptoms. METHODS ----- A randomized controlled study design with a one-year follow-up was used. Fifty patients with mild to moderate depressive symptoms (74% female, aged 57 +/- 9 yrs, diabetes duration of 10 +/- 8 yrs, BMI 31 +/- 6 kg/m2, HbA1C 7.7% +/- 1.4, 53% insulin treated) were randomly assigned to either an intervention or a control group. The intervention group underwent four psycho-educational sessions aimed at enabling self-management of depressive symptoms. The control group was informed about the screening results and depression treatment options while continuing diabetes treatment as usual. Both groups were contacted by phone in 2-3-month intervals, and re-assessed for depression after 6 and 12 months. Changes in depressive symptoms and glycaemic control were considered primary outcomes. Mann-Whitney U test and Friedman ANOVA were used to compare between- and within-group indicators at 6- and 12-month follow-ups. RESULTS ----- Both the intervention and the control group reported a significant decrease in depressive symptoms as measured by the CES-D scale (Friedman ANOVA chi2 = 10.8 p = .004 and chi2 = 7.3 p = 0.03, respectively). The 6-month and 1-year indicators of glycaemic control as compared to baseline HbA1C values were also improved in both groups (chi2 = 11.6 p = 0.003 and chi2 = 17.1 p = 0.0002, respectively). Between-group differences in depressive symptoms and HbA1C values were not statistically significant either at 6- or at 12-month follow-up (all p > 0.05).CONCLUSION ----- Psycho-educational treatment appears to be beneficial in diabetic patients with mild to moderate depressive symptoms, but its effects are comparable with the non-specific support given to the subjects in the control group. TRIAL REGISTRATION ----- Current Controlled Trials ISRCTN58745372.