Dynamic liver CT scanning is used to observe the hemodynamics of hepatic tumor-like lesions by taking images sequentially after administration of contrast media. In this study in dogs, we compared the hemodynamic patterns of hepatocellular carcinoma (HCC), one of the malignant tumors, and nodular hyperplasia (NH), a benign tumor that is more common in older dogs. Thirty-six dogs with HCC and 40 dogs with NH, which were histopathologically diagnosed at Taniura Animal Hospital, were used as subjects. Dynamic CT scanning was performed and the data of each scanning phase were collected. Dilated blood vessels, septum formation, and capsule formation were noted in the tumors from 25, 17, and 25 animals with HCC, respectively. In the arterial phase, high density and low contrast were noted in 8 and 23 dogs, respectively. Low density was noted in 34 dogs in the equilibrium phase. In contrast, no dilated blood vessels, septum formation, or capsule formation was noted in the dogs with NH. High density, low contrast, and low density were noted in 8, 9, and 23 dogs, respectively, in the arterial phase. In the equilibrium phase, the enhancement level was equal to the surrounding liver tissues in all animals. The CT values of HCC in the plain, the arterial phase, portal venous phase and equilibrium phase after the administration of contrast media, were significantly (p < 0.05 to 0.001) lower than those of the surrounding liver tissues. In the arterial phase, the percent incidence of low density was significantly less in HCC than NH, while that of low contrast was significantly greater (p < 0.001) in HCC than NH. Dynamic CT scanning identified differences between the hemodynamics and internal structures of HCC and NH in dogs. Dynamic liver CT scanning can therefore be considered a useful technique in the differential diagnosis of hepatic tumor-like lesions in dogs.