Nanoparticle-based molecular imaging has emerged as an interdisciplinary field which involves physics, chemistry, engineering, biology, and medicine. Single-walled carbon nanotubes (SWCNTs) have unique properties which make them suitable for applications in a variety of imaging modalities, such as magnetic resonance, near-infrared fluorescence, Raman spectroscopy, photoacoustic tomography, and radionuclide-based imaging. In this review, we wilt summarize the current state-of-the-art of SWCNTs in molecular imaging applications. Multi-functionality is the key advantage of nanoparticles over traditional approaches. Targeting ligands, imaging labels, therapeutic drugs, and many other agents can all. be integrated into the nanoparticle to allow for targeted molecular imaging and molecular therapy by encompassing many biological and biophysical barriers. A multifunctional, SWCNT-based nanoplatform holds great potential for clinical applications in the future. (C) 2009 Elsevier Ltd. All rights reserved.