A dynamic computed tomographic (CT) technique for separate quantification of arterial and portal components of liver perfusion with functional imaging was developed and used to study 24 livers. A single-location dynamic sequence was performed after intravenous administration of a 50-mL bolus of contrast medium. The time to maximum splenic enhancement was used to differentiate arterial and portal phases, and the maximal slopes of the liver time-density curve in each phase were used to calculate both arterial and portal perfusion. The arterial/total perfusion ratio was also calculated. The values of these parameters for individual pixels were used to create functional images. Arterial perfusion was increased in patients with metastases and cirrhosis. Portal perfusion was reduced in patients with cirrhosis. Functional images were successfully created in all but one case. The technique enables quantification and functional mapping of several perfusion parameters with a spatial resolution greater than that achieved with other imaging techniques.