This is the first report from Poland documenting biopsy-proven renal diseases in type 2 diabetes mellitus. We analyzed the data of 76 patients with type 2 diabetes who underwent renal biopsy and were diagnosed in the Department of Nephropathology, Medical University of Lodz. The patients were divided into the following three groups according to the histological diagnosis: group I – isolated non-diabetic renal disease (NDRD); group II – NDRD superimposed on underlying diabetic nephropathy (NDRD + DN); and group III – isolated diabetic nephropathy (DN). Non-diabetic renal disease was found in 38 patients (50%), non-diabetic renal disease superimposed on underlying diabetic nephropathy was diagnosed in 11 patients (14.5%), and isolated diabetic nephropathy was seen in 27 patients (35.5%). The most common glomerular lesion found in groups I and II was focal segmental glomerulosclerosis (FSGS). On the basis of clinical and laboratory parameters, differentiating NDRD from DN in diabetic patients is not always obvious. However, our study revealed that hematuria, short duration of diabetes and the absence of diabetic retinopathy in type 2 diabetic patients manifesting renal involvement may suggest NDRD. The only way to distinguish NDRD from DN is histological evaluation of renal tissue.