Objective: To investigate the imaging features and clinical significance of carbon dioxide digital subtraction angiography (CO2-DSA) in the diagnosis and treatment of hepatocellular carcinoma (HCC). Methods: Both CO2-DSA and conventional DSA were performed in all 47 patients with HCC, and the angio-graphic manifestations of CO2-DSA were compared with those of conventional DSA in the same patients. Results: Peripheral arterial and capillary imaging by CO2-DSA was inferior to that by conventional DSA, although blood pools were well visualized with CO2. Improved visualization of arterioportal shunting (APS) was obtained with CO2-DSA compared with that by conventional angiography. APS was observed in 33 cases by CO2-DSA and in 12 cases by conventional angiography (P<0. 001). Retrograde visualization of the portal vein (PV) trunk and its large branches was demonstrated in 16 cases by CO2-DSA and in 1 case by conventional DSA (P<0. 001). The manifestation of lipiodol retention in the tumors was consistent with Objective: To investigate the imaging features and clinical significance of carbon dioxide digital subtraction angiography (CO2-DSA) in the diagnosis and treatment of hepatocellular carcinoma (HCC). Methods: Both CO2-DSA and conventional DSA were performed in all 47 patients with HCC , and the angio-graphic manifestations of CO2-DSA were compared with those of conventional DSA in the same patients. Results: Peripheral arterial and capillary imaging by CO2-DSA was inferior to that by conventional DSA, although blood pools were well visualized with CO2 Improved visualization of arterioportal shunting (APS) was obtained with CO2-DSA compared with that by conventional angiography. APS was observed in 33 cases by CO2-DSA and in 12 cases by conventional angiography (P <0.001). Retrograde visualization of the portal vein (PV) trunk and its large branches were demonstrated in 16 cases by CO2-DSA and in 1 case by conventional DSA (P <0.001). The manifestation of lipiodol retention in the tumors was consistent with