The tri-peptide sequence of arginine-glycine-aspartic acid (RGD) can specifically bind to the integrin αⅤβ3 receptor. Accordingly, a variety of radiolabeled RGD-based peptides have been developed for non-invasive imaging of integrin αⅤβ3 expression via positron emission tomography (PET) or single photon emission computed tomography (SPECT). Among all the RGD radiotracers studied, two PET imaging agents, 18F-Galacto-RGD and 18F-AH111585, have been investigated in clinical trials, and the results demonstrated that both radiotracers allowed the specific imaging of various types of tumors, and the tumor uptake correlated well with the expression of integrin αⅤβ3. Recently, series of RGD dimeric peptides with PEG linkers have been studied. The new types of RGD peptides showed much higher in vitro integrin αⅤβ3-binding affinity than the single RGD tri-peptide sequence, and importantly, they exhibited significantly increased tumor uptake and improved in vivo kinetics in animal models. As a representative, 68Ga-BNOTA-PRGD2 could be easily prepared and exhibited excellent in vivo behaviors in animal models. No adverse reactions are observed in animal models to date.