Transarterial chemo-embolization (TACE) provides a successful treatment mode for some benign or malignant tumors. The success of TACE is largely due to (i), development of excellent instruments and techniques for real-time X-ray imaging, and (ii), advanced catheters which allow for accurate intra-arterial navigation. Further improvements can –most probably- be achieved by enhancing the functionality of the embolic particles. For example, embolic particles can be made radiopaque, which means that they can be visualized in situ through X-ray fluoroscopy and computed tomography (CT). X-ray visibility of the radiopaque 3D-crosslinked methacrylic iodine-containing embolic microspheres of the new embolization product X-Spheres was evaluated. A rabbit cadaver model and stateof-the-art imaging equipment in a hospital setting were used. Clear visibility of the particles was found in CT images, especially if the plane of vision is chosen in such that overlap with bone structures is avoided. Therefore, the use of radiopaque embolic microspheres can provide important and otherwise inaccessible post-procedural information about the efficacy of the procedures.