['Serum levels of des-gamma-carboxy prothrombin (DCP) and alpha-fetoprotein (AFP) are known to be useful tumor markers for the diagnosis of hepatocellular carcinoma (HCC). The aim of this study was to examine the diagnostic efficacy of DCP and AFP in differentiating HCC from chronic liver diseases.', 'We examined 1,377 HCC patients and 355 patients with chronic hepatitis or cirrhosis (non-HCC) who visited our institute and affiliated hospitals between June 1997 and September 2003.', 'The median values of DCP and AFP were 60 mAU/mL and 34 ng/mL in HCC patients, respectively, and 18 mAU/mL and 3 ng/mL in non-HCC patients, respectively. The areas under the receiver operating characteristic (ROC) curves of DCP and AFP were 0.812 and 0.887, respectively (p < 0.0001). The area under the DCP ROC curve was significantly smaller than that of AFP in tumors less than 3 cm in diameter (p < 0.0001). However, the ROC area of DCP was significantly larger than that of AFP in tumors greater than 5 cm in diameter (p < 0.0001).'] Does sensitivity and specificity of des-gamma-carboxy prothrombin for diagnosis of patients with hepatocellular carcinomas vary according to tumor size?