Background. Non-alcoholic fatty liver disease (NAFLD) is becoming the most common cause of chronic liver disease worldwide, affecting up to 30% of population. Non-alcoholic fatty liver disease can lead to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. Age, obesity, insulin resistance, type 2 diabetes, and dyslipidemia are important risk factors for developing hepatic steatosis. Concomitant diseases, especially cardiovascular, are discussed as important causes of death in NAFLD patients.Objectives. The objective of this study was to conduct a retrospective comparison of the frequency of concomitant diseases in NAFLD patients and controls, especially metabolic syndrome and cardiovascular disease (CVD). Material and methods.A total of 1,058 (558 NAFLD patients and 500 controls). Diagnosis of NAFLD was established with ultrasound examination in the absence of other causes of fatty liver. The control group included patients with no history of liver disease, normal liver image in ultrasound examination and normal liver laboratory tests.Results. Overweight and/or obesity were diagnosed in 80.8% of patients in the study group and 40.8% in the controls (p < 0.001). Metabolic syndrome was present in 48.7% patients in the study group compared with 14.4% controls, (p < 0.001). In the study group, we found higher prevalence of hypertension (56. 1% vs 37%; p < 0.001), type 2 diabetes mellitus (24.4% vs 8.6%; p < 0.001), decreased concentration of serum HDL (35. 1% vs 19.5%; p < 0.001), elevated serum triglycerides (36.5% vs 15.4%; p < 0.001). Cardiovascular disease was found in 13.6% of individuals in the study group and in 15% controls (NS, p = 0.32). The most frequent concomitant gastrointestinal disease present in the study group was gastroesophageal reflux disease (GERD) (31.9% vs 22.8%; p < 0.001) followed by colonic diverticulosis (23.7% vs 15.8%; p < 0.005).Conclusions. Metabolic syndrome with its components is more common in NAFLD patients compared to matched controls. Additionally, NAFLD patients are more often affected by GERD and colonic diverticulosis but not by CVD.