AIM: To quantify the circulating DNA in plasma from patients with hepatocellular carcinoma (HCC) and to evaluate its prognostic value.METHODS: Blood samples were collected from 79patients with HCC before operation, 20 patients with liver cirrhosis, and 20 healthy volunteers. Circulating DNA was extracted from plasma and quantified. The association between circulating DNA level and prognosis of HCC patients was evaluated.RESULTS: Compared with the healthy volunteers (17.6± 9.5 ng/mL), a significant higher circulating DNA level was found in the patients with HCC (47.1±43.7 ng/mL, P = 0.000) or with liver cirrhosis (30.0 ± 13.3 ng/mL, P = 0.002). The circulating DNA level was closely associated with tumor size (P = 0.008) and TNM stage (P = 0.040), negatively associated with the 3-year diseasefree survival (DFS) (P = 0.017) and overall survival (OS) (P = 0.001).CONCLUSION: Large or invasive tumor may release more circulating DNA, and higher level of circulating DNA may be associated with poor prognosis of HCC patients.