Cortistatin (CST) is a neuropeptide that strongly resembles somatostatin (SS) structurally and functionally. CST binds to all five SS receptors (SSTR1-SSTR5) with high affinity and exerts its function mainly through SSTRs. Despite many similar functions between these two neuropeptides, they are products of different genes. Recently, some distinct functions and receptor usage of CST have been reported. Some of the interesting functions of CST were not found with SS. Therefore CST could have potential new roles in an ex-neuronal system that regulates immune responses as well as other cellular functions in the body. In this review, we discuss the new functions of CST in the immune system, cancer pathogenesis, and possible CST-specific receptors.