['Increasing evidence suggests that alterations in mitochondrial DNA (mtDNA) copy number (mtDNAcn) and relative telomere length (RTL) may be implicated in the tumorigenesis of several malignancies. Alterations of both RTL and mtDNAcn are generally accepted as independent biomarkers for predicting risk and prognosis in various cancers. The aim of this study was to evaluate the prognostic value of combining leukocyte RTL with mtDNAcn (RTL-mtDNAcn) in hepatocellular carcinoma (HCC).', 'RTL and mtDNAcn in peripheral blood leukocytes (PBLs) were measured using a real-time PCR-based method in a total of 250 HCC patients treated with transcatheter arterial chemoembolization (TACE). We evaluated the associations between RTL and/or mtDNAcn and HCC overall survival using Kaplan-Meier curve analysis and Cox proportional hazards regression model.', 'We found that patients with longer leukocyte RTL or lower mtDNAcn had shorter overall survival time. The univariate analysis (HR\xa01.63, 95\xa0% CI 1.23-2.17, P\xa0=\xa07.7\xa0×\xa010(-4)) and multivariate analysis (HR\xa01.78, 95\xa0% CI 1.31-2.42, P\xa0=\xa02.4\xa0×\xa010(-4)) indicated that longer leukocyte RTL was significantly associated with poorer OS in HCC patients. Kaplan-Meier curve analysis showed that patients with longer RTL had shorter overall survival time than those with shorter RTL (log-rank P\xa0=\xa00.001). Patients with lower mtDNA copy number was significantly associated with poorer OS by Cox proportional hazards model using both univariate (HR\xa01.60, 95\xa0% CI 1.21-2.13, P\xa0=\xa00.001) and multivariate analyses (HR\xa01.77, 95\xa0% CI 1.30-2.41, P\xa0=\xa02.8\xa0×\xa010(-4)). Kaplan-Meier curve analysis showed that patients with lower mtDNA content had significantly shorter overall survival time than those with higher mtDNA content (log-rank P\xa0=\xa00.001). Furthermore, combination of leukocyte RTL and mtDNAcn significantly improved the efficacy of predicting HCC prognosis. Patients with longer RTL and lower mtDNAcn exhibited a significantly poorer overall survival in both the univariate analysis (HR\xa02.21, 95\xa0% CI 1.52-3.22, P\xa0=\xa03.5\xa0×\xa010(-5)) and multivariate analysis (HR\xa02.60, 95\xa0% CI 1.73-3.90, P\xa0=\xa04.3\xa0×\xa010(-6)). The effect on patient prognosis was more evident in patients with longer RTL and lower mtDNAcn than in those with shorter RTL and lower mtDNA (HR\xa02.11, 95\xa0% CI 1.34-3.32, P\xa0=\xa00.001) or in those with longer RTL and higher mtDNA (HR\xa02.10, 95\xa0% CI 1.34-3.27, P\xa0=\xa00.001).'] Are alterations of telomere length and mtDNA copy number associated with overall survival in hepatocellular carcinoma patients treated with transarterial chemoembolization?