Objective To investigate the clinical application of CT perfusion imaging in assessing the hemodynamic changes in patients with small hepatocellular carcinoma (<5 cm) before and after transcatheter arterial chemoembolization (TACE). Methods Twelve patients with small hepatocellular carcinoma were enrolled in this study. CT perfusion imaging of the liver was performed 1 - 2 days before and 3 - 4 weeks after TACE. By using the perfusion parameters the hemodynamics of the preoperative and postoperative tumor tissue, the hemodynamics of the preoperative tumor tissue and the normal tissue, and the hemodynamics of the postoperative active tumor tissue and the normal tissue were determined , and the results were compared between each other. Results Before TACE, the blood flow (BF), hepatic arterial fraction (HAF), hepatic arterial perfusion (HAP) and permeability of surface (PS) in the tumor tissue were significantly higher than those in the normal tissue (P < 0.01), while after TACE all the perfusion parameters except blood volume (BV) were significantly decreased in the tumor tissue (P < 0.01). After TACE, BF, PS, HAF and HAP in the activity tumor tissue were increased more than those in the normal tissue (P < 0.05). Conclusion CT perfusion imaging is of great clinical value in diagnosing < 5 cm hepatocellular carcinoma , in evaluating the hemodynamic changes after TACE and in demonstrating the activity of the residual tumor tissue.