Quantum dots (QDs) have shown promise as imaging agents in cancer, heart disease, and gene therapy research. This review focuses on the design of QDs, and modification using peptides and proteins for mediated targeting of tissues for fluorescence imaging of tumors in vivo. Recent examples from the literature are used to illustrate the potential of QDs as effective imaging agents. The distribution and ultimate fate of QDs in vivo is considered, and considerations of designs that minimize potential toxicity are presented.