Accurate 3D tumoral volume evaluation is now possible through the combined use and progress of computer graphics technics (3D reconstruction and visualization) and medical imagery (helicoidal TDM scanner). Specific organ and pathology oriented softwares can help answer rapidly to problems posed by oncologic praticians. A new decision support for diagnosis, therapy and follow-up is emerging. First results in liver tumors and hepatic regeneration macroscopic biometrics are presented. Tumoral or organ volumic index will be usable in the follow-up. TNM staging, external conformal radiotherapy for prostatic or brain tumors, drugs cytolytic effects evaluation will take great advantage of these technologies. 3D visualization and matching CT and MRI imagery can help computed assisted surgery.