The aims of this cohort study were to evaluate the association of malignant lymphoproliferative disorders in patients with chronic viral hepatitis and to compare the results with those in individuals with non-alcoholic fatty liver disease. A total of 3,873 patients with chronic liver disease who were seen consecutively in the Liver Disease Outpatient Clinic between January 2001 and July 2007 were assessed retrospectively. The frequency of malignant lymphoproliferative disorders including non-Hodgkin's lymphoma, Hodgkin's lymphoma, and chronic lymphocytic leukemia in these patients was investigated. Of the total, 1,999 patients had chronic hepatitis B infection (male/female: 1,226/773, mean age: 45.1 ± 13.2 years), 978 had chronic hepatitis C infection (male/female: 437/541, mean age: 53.8 ± 13.7 years), and the remaining 896 had non-alcoholic fatty liver disease (male/female: 450/446, mean age: 50.8 ± 11.2 years). A malignant lymphoproliferative disorder was identified in 13 patients (male/female: 9/4, mean age: 52.8 ± 16.8 years) with chronic viral hepatitis, while no case of malignant lymphoproliferative disorder was identified in individuals with non-alcoholic fatty liver disease (P = 0.048). Among the patients with malignant lymphoproliferative disorders, seven had chronic hepatitis B infection and six had chronic hepatitis C infection; 11 had non-Hodgkin's lymphoma and two had chronic lymphocytic leukemia. All non-Hodgkin's lymphoma cases were B-cell lymphoma. Based on the data obtained in this investigation, the association with malignant lymphoproliferative disorders in chronic viral hepatitis seems to be high as compared to that occurring in individuals with non-alcoholic fatty liver disease. J. Med. Virol. 83:974–980, 2011. © 2011 Wiley-Liss, Inc.