Abstract: ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET imaging monitoring tumor response in patients undergoing ehemo-and radiotherapy and differentiation residual or recurrent viable tumor and therapy-induced fibrosis or scar tissue has been documented for various solid tumors. Furthermore, there are now several reporis suggesting that quantitative assessment of therapy-induced changes in tumor ¹⁸F-FDG uptake may allow prediction of tumor response and patient outcome very early in the course of therapy. In nonresponding patients, trcatnlent may be adjusted according to the individual chemo-and radiosensitivity of the tumor tissue. Early prediction of tumor response to ehenlotherapy and radiotherapy by ¹⁸F-FDG PET has enormous potential to "personalize" treatment and to reduce the side-effects and costs of ineffective therapy.