Small hepatic nodular lesions are frequently detected by ultrasonography in patients with liver cirrhosis during follow-up. However, hepatocellular carcinomas (HCCs) and non-HCC nodules are difficult to differentiate by ultrasonography because they have a similar appearance. We used color Doppler ultrasonography (CDU) to examine 29 HCCs and 26 non-HCC nodules less than 2 cm in diameter to determine whether CDU can be used to differentiate small hepatic nodules. There were no significant differences between the examined HCCs and non-HCC nodules with regard to ultrasonographic appearance, i.e., hypoechoicity or hyperechoicity. Blood flow signals were detected in a significantly higher percentage of HCCs (13 of 29, 44.8%) than in non-HCC nodules (2 of 26, 7.7%; P<0.005), although the sensitivity was low. Therefore, we classified nodules as hypoechoic or hyperechoic by B-mode ultrasonography and examined their blood flow signals. Among nodules that were hypoechoic, signals were detected in a significantly higher percentage of HCCs (12 of 18, 66.7%) than in non-HCC nodules (2 of 13, 15.4%; P<0.005). In contrast, among hyperechoic nodules, signals were detected in only 1 of 11 (9.1%) HCCs and in 0 of 13 non-HCC nodules. Our results suggest that examination of blood flow by CDU is useful for differentiating small hepatic nodules, especially hypoechoic nodules.