BACKGROUND/AIMS: Focal nodular hyperplasia (FNH) is a benign hepatic tumor with few serious complications and no malignant transformation. However, differential diagnosis between FNH and other liver tumors, especially hepatocellular carcinoma, is often difficult. METHODS: Clinical features of surgically resected FNH were reviewed. From January, 1995 to February, 2003, 10 patients with surgically resected FNH were enrolled. Their age, sex, results of laboratory examination, imaging studies and pathologic findings were evaluated. RESULTS: Median age was 37.5 years and sex ratio (male:female) was 1.5:1. In 5 cases, resection to exclude hepatic adenoma or HCC was performed. Four cases were diagnosed incidentally after surgery. Four patients had risk factors for HCC, such as hepatitis B virus infection, liver cirrhosis or both. The size of FNH was 3.2 +/- 2.2 cm. The most common site of the tumor was segment 6 (30.0%). Differential diagnosis with HCC was difficult in 5 of six cases in whom CT was performed. Although needle biopsies were performed preoperatively in 4 cases, it was difficult to distinguish FNH from hepatic adenoma or HCC. CONCLUSIONS: FNH was resected due to uncertainty of diagnosis, or incidentally during hepatectomy in patients with other liver disease. In the former, differential diagnosis with hepatic adenoma or HCC was a major problem despite extensive work-up including dynamic CT or biopsy.