ObjectiveTo discuss the CT imaging differences between mass-forming intrahepatic cholangiocarcinoma (ICC) and poorly-differentiated hepatocellular carcinoma (HCC). MethodThe clinical and CT data of 28 patients with mass-forming ICC (mass-forming ICC group) and 27 patients with poorly-differentiated HCC (poorly-differentiated HCC group), who were confirmed by pathological diagnosis in the West China Hospital from February 2014 to August 2014, were collected and analyzed retrospectively. ResultsThe contour, margin, enhancement patterns in the arterial phase and portal vein phase of the tumor had significant differences between the mass-forming ICC group and poorlydifferentiated HCC group (P < 0.05), in other words, the lobulated shape (15/28, 53.6%), indistinct margin (17/28, 60.7%), peripheral enhancement in the arterial phase (21/28, 75.0%) and prolonged enhancement in the portal vein phase (14/28, 50.0%) were more often seen in the mass-forming ICC group, while the poorly-differentiated HCC group were mainly the round shape (17/27, 63.0%), partially well-defined margin (18/27, 66.7%), diffuse heterogeneous enhancement in arterial phase (20/27, 74.1%) and wash out in the portal vein phase (18/27, 66.7%). The presence of bile duct dilatation in the the mass-forming ICC group was significantly higher than that in the poorly-differentiated HCC group﹝57.1% (16/28) versus 14.8% (4/27), P=0.001﹞. The size and enhancement degree of lymph node in the mass-forming ICC group were significantly bigger or higher than those in the poorly-differentiated HCC group (average lymph node size: 1.7 cm versus 1.3 cm, P=0.009; average enhancement degree of lymph node: 62.6 HU versus 51.8 HU, P=0.031). ConclusionCT features, such as tumor contour, margin, enhancement characteristics, the presence of bile duct dilatation, and the size and enhancement degree of lymph node, might help for differentiating mass-forming ICC from poorly-differentiated HCC, so that more timely selection of appropriate treatment strategies would be made.