Qualitative and quantitative multimodality imaging play a more and more important role in the planning, quality control, and assessment of response in many oncologic and non oncologic diseases. Before hybrid modalities such as SPECT/CT, PET/CT and, most recently, PET/MRI, became available, the images from the different modalities were analyzed independently or by software fusion. Nowadays, these images are most frequently acquired on hybrid modalities, allowing for so called "one-stop-shop" investigations. Depending on a static or a dynamic image acquisition, either semi or fully quantitative measurements of both structural and functional parameters are possible, allowing for multi-parametric image analysis. These qualitative and quantitative parameters can then be used for detection and assessment of extension of disease as well as for planning of therapeutic interventions or, even more interesting, for quality control, dosimetry of radionuclide therapies, assessment of response to treatment and, finally, prediction of outcome of the patients. This thesis discusses the qualitative and quantitative imaging and quantification methods available today and their potential future impact in research and clinical decision making.