AIM The aim of this study is to clarify the efficacy of angio-helical CT and CT-fluoloscopic marking for diagnosis of metastatic liver cancer. PATIENTS AND METHODS Seventy eight patients with metastatic liver cancer were enrolled whose image findings were confirmed with operation. They consisted of 2 groups, 14 cases (33masses) performed angio-helical CT and 64 cases (135masses) not performed. Angio-helical CT means helical CT during both hepatic arteriography (CTA) and arterial portography (CTAP). CT-fluoloscopy provides real time CT image obtained from rapid reconstruction of sequential scanning data which facilitates puncture to proper sites and marking with micro vascular coil. RESULTS (1) The overall detectability for metastatic liver cancer with conventional imaging modalities (CT, US, MRI, Angiography) was 59.4%. The detection rate for masses smaller than 1.5cm was 28% whereas the rate for those larger than 1.6cm reached 91.8%. (2) The sensitivity of angio-helical CT was favorable (90.9%) in contrast with those of CT, US, MRI and Angiography (45.5%, 42.4%, 39.4%, 57.6%, respectively). Angio-helical CT could detect 84.2% of masses smaller than 1.5cm. Furthermore, 93.8% of lesions showing ringed enhancement with CTA were proved to be metastatic lesions suggesting the usufulness of CTA to differentiate lesions. (3) Of the 47 lesions diagnosed as metastasis with angio-helical CT, 17 (36.2%) were regarded as false positive lesions. However, this high rate was attributed to lesions smaller than 1cm showing solid enhancement with CTA which might be missed during operation. For further evaluation of such lesions it is mandatory to develop the method to identify minute lesions exactly. (4) We employed CT-fluoloscopic marking for this purpose. This approach has hitherto elucidated the histology of 3 minute lesions(metastasis, hemangioma and grauloma) and is expected to disclose the significance of lesions showing solid enhancement with CTA. CONCLUSION Angio-helical CT combined with CT-fluoloscopic marking affords the best diagnostic ability for metastatic liver cancer.