AIM: To investigate the microcirculation changes in liver of patients with tumor during chemotherapy by perfusion computed tomography (CT). METHODS: Sixty patients with tumor and 20 controls were enrolled in this study. Perfusion CT parameters of patients and controls were compared, including hepatic perfusion index (HPI), mean transit time (MTT), and permeability-surface area product (PS). Correlation between perfusion CT parameters, treatment cycle and alanine aminotransferase (ALT) level was studied. RESULTS: No difference was found in HPI (25.68% ± 7.38% vs 26.82% ± 5.13%), MTT (19.67 ± 5.68 s vs21.70 ± 5.43 s) and PS (17.00 ± 4.56 mL/100 mL per min vs 19.92 ± 6.35 mL/100 mL per min) between pa- tients and controls. The HPI and MTT were significantly higher in patients undergoing 2 cycles of chemotherapy than in controls and those undergoing 1 cycle of che- motherapy (29.76% ± 5.87% vs 25.68% ± 7.38% and 25.35% ± 4.05%, and 25.61 ± 5.01 s vs 19.67 ± 5.68 s and 19.74 ± 4.54 s, respectively, P < 0.05). The HPI was higher in patients with hepatic steatosis than in controls and those without hepatic steatosis (30.85% ± 6.17% vs 25.68% ± 7.38% and 25.70% ± 4.24%, P < 0.05). Treatment cycle was well correlated with HPI and MTT (r = 0.40, r = 0.50, P < 0.01). ALT level was not correlated with perfusion CT parameters. CONCLUSION: HPI and MTT are significantly increased in patients with tumor during chemotherapy and well correlated with treatment cycle. Chemotherapy affects hepatic microcirculation in patients with tumor. Changes in hepatic microcirculation can be quantitatively assessed by perfusion CT. AIM: To investigate the microcirculation changes in liver of patients with tumor during chemotherapy by perfusion computed tomography (CT). METHODS: Sixty patients with tumor and 20 controls were enrolled in this study. Perfusion CT parameters of patients and controls were compared, including hepatic Correlation between perfusion CT parameters, treatment cycle and alanine aminotransferase (ALT) level was studied. RESULTS: No difference was found in HPI (HPI), mean transit time (MTT), and permeability- 25.68% ± 7.38% versus 26.82% ± 5.13%), MTT (19.67 ± 5.68 s vs21.70 ± 5.43 s) and PS (17.00 ± 4.56 mL / 100 mL per min vs 19.92 ± 6.35 mL / 100 mL per min) pa- tients and controls. The HPI and MTT were significantly higher in patients undergoing 2 cycles of chemotherapy than in controls and those going one cycle of che- motherapy (29.76% ± 5.87% vs 25.68% ± 7.38% and 25.35% ± 4.05% , and 25.61 ± 5.01 s vs 19.67 ± 5.68 s and 19.74 ± 4 .54 s, respectively, P <0.05). The HPI was higher in patients with hepatic steatosis than in controls and those without hepatic steatosis (30.85% ± 6.17% vs 25.68% ± 7.38% and 25.70% ± 4.24%, P <0.05 ). Treatment cycle was well correlated with HPI and MTT (r = 0.40, r = 0.50, P <0.01). CONCLUSION: HPI and MTT were significantly increased in patients with tumor during chemotherapy and well correlated with treatment cycle. Chemotherapy Effects hepatic microcirculation in patients with tumor. Changes in hepatic microcirculation can be quantitatively assessed by perfusion CT.