Diagnosis and therapy of disease have undergone significant improvement, especially in the field of medical imaging. In the last decades, large scale research has sparked impressive progression in both technical possibilities and clinical knowledge. Unfortunately, these two factors have not always evolved in parallel. The discrepancy between technical advances and supporting evidence has been particularly large in the field of medical imaging. Experimental imaging may be justifiable in a research setting, but large-scale implementation of new techniques in clinical practice needs to be supported by proper validation, and scientific evidence of the benefit. The status of recent advances in the fields of molecular and multimodality medical imaging, with an emphasis on cancer in the head and neck area and on liver metastases, is discussed in this thesis.