Fatty liver in obese patients is emerging as one of the most common causes of chronic liver disease. Obese patients are at risk of developing type 2 diabetes mellitus (DM), and aggravating non-alcoholic fatty liver disease (NAFLD), developing into steatohepatitis (NASH) and hepatic fibrosis. Little is known of the possible impact on liver fibrogenesis of diabetes type 2 associated with obesity and NAFLD. Fifty-two morbidly obese patients were evaluated with complete clinical and laboratory medical assessment. Liver biopsy material was fixed in formalin, routinely processed to paraffin blocks, cut into 4-microm sections, stained with HE, PAS, Masson's trichrome and reticulin. Immunohistochemical stains included collagen IV, SMA and laminin. Within the initial group of 52, 25 patients had DM type 2, mean age 45.8 years. Patients with diabetes were older; had higher BMI, liver enzyme tests, glucose, cholesterol, and triglycerides; and lower albumin concentration. Livers of diabetics had significantly more severe steatosis and rich perisinusoidal collagen IV, laminin and SMA accumulation without histologically detectable NASH and irrespective of the degree of steatosis. Obese patients with type 2 DM and insulin resistance develop more severe NAFLD and early sinusoidal fibrosclerosis.