On the case of 62 year old patient with diabetes type 2 complicated by diabetic nephropathy, we present diagnostic and therapeutic problems of severe nephrotic syndrome caused by membranous nephropathy confirmed by renal biopsy superimposed on diabetic nephropathy. Special attention was paid to the difficulties in achievement the remission of nephrotic syndrome with typical pharmacological treatment and necessity of using drastic form of treatment which was bilateral embolisation of renal arteries and subsequent continuous renal replacement therapy.