Patients with malignant tumors originating from the biliary tree have a poor prognosis, since only a minority of tumors can be resected and most palliative regimens have shown only limited success. We present two patients with unresectable tumors, who were treated with trans-arterial (90)yttrium radioembolization: a patient with an infiltrating gallbladder carcinoma and a patient with an extensive intrahepatic cholangiocarcinoma. In both cases the treatment was technically feasible, effective in controlling tumor growth, and without significant side effects. In conclusion, the presented cases demonstrate the potential of (90)yttrium radioembolization as a palliative treatment option for malignant tumors of the biliary tree.