The application of nanotechnology in non-invasive diagnosis comprises many fi elds such as diagnostic radiology (i.e. Computed tomography (CT), and nuclear medicine [i.e. Radionuclidic Imaging, Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET)] for imaging, characterization, staging and therapy monitoring. Medical diagnostic imaging requires accumulation of contrast agent in the target site, often achieved most effi ciently by steering targeted nanoparticles containing contrast agent into the target. For imaging modalities with low sensitivity, nanoparticles bearing multiple contrast groups provide signal amplifi cation. The materials used to synthesize diagnostic nanoparticles include lipids, polymers, and metals. Signal generators incorporated into nanoparticles include iodine, gold, bismuth, and radionuclides. Recently, multimodal imaging techniques such as SPECT/CT, PET/CT, and SPECT/CT/MRI are becoming popular as imaging modalities depending on the ability to detect functional information and anatomical information about the disease within a single imaging procedure in less time.