PURPOSE: The diagnosis of Budd-Chiari syndrome on CT is difficult if CT do not demonstrate obstruction of the IVC or hepatic vein and other parameter is needed for the correct diagnosis. The purpose of our study was to determine the usefulness of measuring the diameter of azygos-hemiazygos vein on CT to differentiate Budd-Chiari syndrome from advanced liver cirrhosis. MATERIALS AND METHODS: Fourteen patients who were proven as Budd-Chiari syndrome on vena cavography were studied for analysis. All patients showed evidence of liver cirrhosis on CT. As a control group fifteen cases of advanced liver cirrhosis who underwent endoscopic sclerotheraphy due to esophageal variceal bleeding were also included for comparison. The largest short axis diameter of azygos-hemiazygos vein was measured in all patients at the level of diaphragm on axial CT and the results were compared in both groups. RESULTS: In patients with Budd-Chiari syndrome the largest short axial diameter of azygos-hemiazygos vein ranged from 0.5cm to 2.5cm(mean ;1.5cm). Only one patient who showed hepatic venous obstruction demonstrated a diameter of less than 1 cm(0. Scm). In contrast, the diameter in patients with advanced liver cirrhosis without obstruction of IVC or hepatic vein was less than 1 cm with a range from 0.2cm to 1 cm(mean ;0.6cm). CONCLUSION: The short axis diameter of azygos-hemiazygos vein was an indicator of IVC obstruction (Budd-Chiari syndrome).