Rotational C-arm angiographic computed tomography (CT) with a flat-panel radiography unit permits three-dimensional (3D) reconstruction of soft tissues and blood vessels. The usefulness of this C-arm technique during transcatheter arterial chemoembolization (TACE) is unknown. The authors analyzed the role of the C-arm technique in 18 patients with unresectable liver tumors during TACE. The technique altered the catheter position anticipated by attending interventional radiologists in seven of the 18 patients (39%; 95% confidence interval [CI]: 20%, 61%) and improved the diagnostic confidence in the selected catheter position in 14 of the 18 patients (78%; 95% CI: 55%, 91%). The technique provides CT-like images that are useful to interventional radiologists during TACE.