Objective To investigate the effect of the adaptive statistical iterative reconstructions (ASIR) on image quality in portal venography by dual energy CT (DECT) imaging. Materials and Methods DECT scans of 45 cirrhotic patients obtained in the portal venous phase were analyzed. Monochromatic images at 70keV were reconstructed with the following 4 ASIR percentages: 0%, 30%, 50%, and 70%. The image noise (IN) (standard deviation, SD) of portal vein (PV), the contrast-to-noise-ratio (CNR), and the subjective score for the sharpness of PV boundaries, and the diagnostic acceptability (DA) were obtained. The IN, CNR, and the subjective scores were compared among the four ASIR groups. Results The IN (in HU) of PV (10.05 +/- 3.14, 9.23 +/- 3.05, 8.44 +/- 2.95 and 7.83 +/- 2.90) decreased and CNR values of PV (8.04 +/- 3.32, 8.95 +/- 3.63, 9.80 +/- 4.12 and 10.74 +/- 4.73) increased with the increase in ASIR percentage (0%, 30%, 50%, and 70%, respectively), and were statistically different for the 4 ASIR groups (p<0.05). The subjective scores showed that the sharpness of portal vein boundaries (3.13 +/- 0.59, 2.82 +/- 0.44, 2.73 +/- 0.54 and 2.07 +/- 0.54) decreased with higher ASIR percentages (p<0.05). The subjective diagnostic acceptability was highest at 30% ASIR (p<0.05). Conclusions 30% ASIR addition in DECT portal venography could improve the 70 keV monochromatic image quality.