Cognitive Radio Networks (CRN) in wireless technology utilizes available spectrum space form the primary users (PU) to serve for secondary users(SU) needs. Dynamic allocation of spectrum in CRN and changes in topology makes challenges in clustering. Clustering allows CRN to achieve scalability and stability in performance of networks. This paper reviews the clustering algorithms and challenges in clustering for CRNs. © 2020 Innovare Academics Sciences Pvt. Ltd. All rights reserved.