Herein, we present the diagnostic efficacy of various imaging diagnostic techniques for small liver cancer(HCC) and HCC occurrence predictability by ultrasonography during the follow-up period of chronic liver diseases. During the recent 4 years, 78 nodules of small liver cancer measuring 2 cm or less in diameter were found in 50 patients with liver cirrhosis. In this study, the tumor size was divided into 2 groups; 1.5 cm or less in maximal diameter (group A) and 1.6 to 2 cm (group B). The tumor detectability of ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI), angiography and lipiodol CT in group A vs group B was 96% vs 97%, 68% vs 88%, 65% vs 94%, 12% vs 78% and 38% vs 89%, respectively. Therefore, angiography and lipiodol CT were not effective for detection of small HCCs smaller than 1.5 cm. Recently, helical CT scanning has been induced in the diagnosis of HCCs and the tumor detectability was enhanced to 82% even in group A. Additionally, helical-dynamic CT has some advantages in evaluating vascularity, especially arterial feeding which is a specific finding to HCCs. In comparison with contrast-enhanced US using CO2-microbubbles, helical-dynamic CT had equivalent accuracy in diagnosing hypervascular tumors, while hypovascular masses were observed in about 30% of group A. With respect to prediction of HCC occurrence in cirrhotic liver, sonographic evaluation of liver parenchyma seemed to be an important parameter.(ABSTRACT TRUNCATED AT 250 WORDS)