Antibodies have attained a central role as targeted therapeutics, with several significant drugs on the market and many more in clinical development for oncological applications. Expansion of the role of antibodies in cancer imaging has been accelerated by a number of factors, including the recognition that antibodies can provide a powerful class of molecular imaging probes for interrogating cell surfaces in vivo. Identification of relevant cell surface biomarkers as imaging targets, coupled with advances in antibody technology, facilitate the generation of antibodies optimized for noninvasive imaging. Developments in imaging instrumentation and radionuclide availability have paved the way for broader evaluation and implementation of radioimmunoscintigraphy and immunoPET. Antibody imaging can provide a sensitive, noninvasive means for molecular characterization of cell surface phenotype in vivo, which can in turn guide diagnosis, prognosis, therapy selection, and monitoring of treatment in cancer.