In cancer treatment, molecular targeting therapy has rapidly progressed. With the improvement of molecular targeting therapy, the need for evaluating bio-marker is increasing. To decide appropriate target agent, evaluating the status of target molecule is mandatory. Anti-angiogenic therapy is widely used as a clinical strategy for cancer treatment such as colorectal cancer, lung cancer. In case of anti-angiogenic treatment, angiogenesis imaging could select the patients who respond to anti-angiogenic treatment. There are several methods to evaluate angiogenesis. Angiogenesis could be evaluated by vascular structure, hemodynamic changes. However, none of those parameters are present in the angiogenic activity of tumor. Furthermore, the results of vascular structure or hemodynamic changes could not predict the response. RGD peptide is a ligand of integrin αvβ3 which over-expresses on the endothelium of neo-vascularization. Using radiolabeled RGD PET, we could evaluate the angiogenic activity of tumor, and it could be related with the response to antiangiogenic drugs. In this paper, we summarized the factors predicting the response. In this paper, we also introduced our preliminary experience of 68Ga-RGD PET in patients with colorectal cancer.