Our objective was to assess the ability of dual-phase helical CT (DHCT) to predict resectability of carcinoma of gallbladder (CaGB). Thirty-two consecutive patients suspected of having CaGB on clinical examination and sonography presented to our centre over 10-month period. All these 32 patients underwent DHCT. Fifteen patients were considered inoperable and 2 had xanthogranulomatous cholecystitis. The remaining 15 patients (10 women, 5 men; age range 33-72 years) underwent surgery and had histopathological confirmation of CaGB and were included in the study based on the following criteria: presence of mass in gallbladder fossa on sonography and DHCT, and confirmation at surgery and histopathological examination. Axial reconstructions of 2 mm were obtained (collimation 3 mm, table speed 4.5 mm/s) for arterial (scan delay 20 s) and venous (scan delay 60 s) phases on a helical scanner. The criteria used for unresectability were: distant metastasis (liver, peritoneum, lymph nodes), extensive local contiguous organ spread, involvement of secondary biliary confluence of both lobes of liver, tumoral invasion of main portal vein, or proper hepatic artery or simultaneous invasion of one side hepatic artery and the other side portal vein. The CT findings related to unresectability were correlated with surgical findings. On the basis of CT findings, 10 patients were unresectable and 5 were resectable. Of the 10 patients considered unresectable, 9 had tumours that were unresectable at surgery (sensitivity 100%, positive predictive value 90%). Five patients had more than one reason and 4 had one reason alone for being unresectable (lymph nodes, n=2; hepatic metastasis, n=1; and vascular invasion, n=1). All 5 patients considered resectable based on CT findings had resectable tumours at surgery (negative predictive value 100%). The overall accuracy of CT was 93.3%. Dual-phase helical CT comprehensively evaluates CaGB and may be a useful tool in preoperative staging of this tumour in determining resectability.