PURPOSE: To verify the usefulness of left portal vein angle (LPVA) on CT scan in the diagnosis of liver cirrhosis and to compare its diagnostic value with that of caudate to right lobe ratio (C/RL ratio). MATERIALS AND METHODS: LPVA, an angle formed by a vertical line and a line connecting the center of the vertebral body to the umbilical point of the left portal vein, and C/RL ratio were measured on CT scans of 100 cirrhotic and 100 normal livers. Diagnostic values of LPVA and C/RL ratio were compared statistically. RESULTS: The mean of LPVA was 18.9 degrees(SD; 7.6) for normal livers and 25.8 degreesSD; 8.4) for cirrhotic livers (P<0.001). The mean of C/RL ratio was 0.47(SD; 1.10) for normal livers and 0.58(SD;0.14) for cirrhotic livers (P<0.001). When LPVA was greater than 30 degreesliver cirrhosis was diagnosed with 36% sensitivity and 92% specificity. When C/RL ratio was greater than 0.60, the diagnose of liver cirrhosis was with 41% sensitivity and 90% specificity. There was no significant difference of the diagnostic accuracy between LPVA and C/R L ratio in ROC analysis. CONCLUSION: Both LPVA and C/RL ratio are useful diagnostic indices of liver cirrhosis on CTscan. LPVA is more convenient to measure than C/RL ratio.