Imaging in Oncology is rapidly moving from the detection and size measurement of a lesion to the quantitative assessment of metabolic processes and cellular and molecular interactions. Increasing insights into cancer as a complex disease with involvement of the tumor stroma in tumor pathobiological processes have made it clear that for successful control of cancer, treatment strategies should not only be directed at the cancer cells but should also take aspects of the tumor microenvironment into account. This requires an understanding of the complex molecular and cellular interactions in cancer tissue. Recent developments in imaging technology have increased the possibility of imaging various pathobiological processes in cancer development and response to treatment. For computed tomography (CT) and magnetic resonance imaging (MRI), various improvements in hardware, software, and imaging probes have lifted these modalities from classical anatomical imaging techniques to techniques suitable for imaging and quantifying various physiological processes and molecular and cellular interactions. Next to a more general overview of possible imaging targets in oncology, this chapter provides an overview of the various developments in CT and MRI technology and some specific applications.