Background. Measurement of urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) has recently become more popular as a means of assessing oxidative stress in the human body. The aim of this study is to compare the levels of urine 8-OHdG in patients with type 2 diabetes with and without nephropathy and to evaluate its role as a biochemical marker for distinguishing these patients from healthy and patients without complications. Methods. For this purpose, 52 patients with type 2 diabetes mellitus (32 with nephropathy (DMN), 20 without nephropathy (DM)) and 20 healthy control subjects (C) were included in this study. The urine concentrations of 8-OHdG were measured by modified LC-MS/MS method and compared with the first morning voiding urine albumin/creatinine ratio (UACR) and HbA1c values of the same patients. Results. The concentrations of urine 8-OHdG in DMN and DM patients were higher than those of the control subjects (3.47 +/- 0.94, 2.92 +/- 1.73, 2.1 +/- 0.93 nmol/mol creatinine, respectively). But there was no statistical difference between DMN and DM (p = 0.115). There is significant correlation between urinary 8-OHdG and UACR (r = 0.501, p <= 0.001). According to ROC analysis, the AUC value of HbA1c was higher than the value of the AUC of 8-OHdG (0.882 and 0.771, respectively). Conclusions. This study shows that the urine 8-OHdG levels increase in diabetic patients. However, urinary 8-OHdG is not a useful clinical marker, compared with UACR, to predict the development of diabetic nephropathy in diabetic patients.