Objective To evaluate the double-arterial phase and portal venous phase scanning in the detection of hepatocellular carcinoma with multi-slice sprial CT (MSCT).Methods Ninety-four patients with hepatocellular carcinoma were examined by abdominal plain CT and early areterial phase (EAP),late arterial phase(LAP),portal venous phase(PVP).Contrast agent of 100 ml (300 mg I/ml) was administrated intravenously by 3 ml/s,for scanning of EAP at 20 to 22 s,LAP at 34 to 37s.and PVP at 60 s.Chi-square test was carried out to compare the sensitivity among various phases.Resuits A total 0f 318 1esions was detected pathologically,with 86 lesions less than 3 cm in size and 232 lesions more than 3 cm.For the early arterial phase,late artefial and portal venous phase,the sensitivity was 39.5%(34),67.4%(58),44.2%(38)respectively for the small tumors,which showed significant differences between phases(X2=15.38,P<0.01).For the large tumors,the sensitivity was 89.6%(208),99.6%(231), 99.1%(230),respectively(X2=39.09,P<0.01).All had positive predictive values of 100%.If the tumors were taken together,the sensitivity was 76.1%(242),90.9%(289),84.3%(268).and the positive predictive value was 88.3%(242/274),86.3%(289/335),93.7%(268/286)for the early arterial phase,late arterial and portal venous phase respectively.There was significant difference of sensitivity and positive predictive value between phases(X2=25.62,9.29,P<0.05).Conclusion Double-arterial phase could improve the detection of tumors,especially for small hepatocellular earcinoma. and late arterial phase scanning is particularly important.