While conventional chemotherapy regimens aim to be cytotoxic against proliferating cells, molecular targeted therapies are directed at specific cancer-associated pathways. To optimize cancer care, an early evaluation of treatment response is warranted for any tumor type - and for any treatment – by using conventional imaging modalities such as ultrasound, CT and MR, FDG-PET or specific radiotracer. FDG-PET is one of the most extensively and successfully used imaging modalities to achieve an early response evaluation. A high SUV-value is a surrogate for malignancy in terms of cancer care and a decrease in FDG-uptake after therapy is associated with treatment response and a favorable clinical outcome. Anyhow, the potential of PET reaches further. By providing metabolic information PET (with or without CT) can help to select patients for targeted therapy and to adapt treatment protocols. PET with FDG and maybe other, more specific PET tracers, promises to direct in a better way personalized cancer care and thus promote translational research. An interesting aspect of molecular imaging is the ability to achieve knowledge on distribution and expression levels of a given receptor. Hereby, imaging could help in guiding systemic treatment given a broad spectrum of radiotracers, detecting specific mutations at molecular level in vivo. From an oncologists point of view the concept of ‘personalized medicine’ should evolve to include ‘personalized imaging’ as well as ‘personalized treatment’ in order to optimize cancer care, reduce side effects and improve quality of life for cancer patients.