Patients affected by liver cirrhosis with and without hepatocellular carcinoma (HCC) underwent galactose testing for the assessment of both quantitative liver function and effective blood flow. The galactose elimination capacity (GEC), when investigating the former parameter, resulted in being significantly reduced in cirrhotics (29.5%) and in cirrhotics with HCC (42.9%) when compared to controls. The galactose clearance, expressing the effective blood flow through the liver, showed a significant decrease (34.0%) only in the group with superimposed HCC. Our results pointed out a significant impairment of effective hepatic blood flow and an overall reduction of hepatic metabolic activity in the cirrhotics with HCC. These data suggest that lower amounts of chemotherapeutic agents must be given to patients affected by cirrhosis with HCC, especially when dealing with substances mainly metabolized by the liver. On the basis of our results, such a reduction was evaluated to be around 50% of the total dosage.