Portal flow in the hepatic nodules is known to decrease during progression to hepatocellular carcinoma. We assessed the reduction in portal flow of the 37 hepatic nodules using the time-density curve of a single-level dynamic CTAP and expressed the results numerically. Retention of the portal flow was classified as three levels: good, moderate and almost zero, the last of which was considered to correspond to classical hypervascular hepatoma. Rather poor retention of portal flow may be an early signal that progression to hypervascular tumor is imminent. This numeric information may be help determine the most appropriate timing for the treatment of hepatic cancerous tumors.