Hilar cholangiocarcinoma (also called Klatskin's tumor) is more common than peripheral cholangiocarcinoma. Sonography, CT, MR imaging, angiography, and cholangiography can suggest the diagnosis, but the major issue of imaging with this tumor is to determine whether the tumor is resectable. The anatomic location of hilar cholangiocarcinoma makes resection difficult, so that surgical exploration of patients with this condition should be undertaken only when preoperative evaluation has shown a potential for curative resection. Preoperative assessment of resectability of hilar cholangiocarcinoma is often extensive, requiring several types of imaging. This pictorial essay reviews the imaging features of hilar cholangiocarcinoma. The role of imaging in the preoperative planning, with specific emphasis on staging extent of disease, including hepatic and vascular involvement, is discussed and illustrated.