The attractive features of Internet of Things (IoT) and the concept of cognitive radio have raised the opportunity of creating a smart world. The advancement of cost-effective technologies and protocols empower us to make practical implementation of IoT which impact on human lifestyle, business and industries. Research interest has thus been dragged into the IoT domain to exploit its potential. However, the increased number of devices have caused the spectrum crisis issue. To mitigate this crisis, Cognitive Radio (CR) technology is integrated with IoT that can search for the available spectrum and reuse it for communication. By using cognitive capabilities, cognitive radio can avoid collision among the network elements to ensure better connectivity, accessibility, scalability and reliability of the IoT system. Currently, the research on CR-IoT is at its early stage. This chapter attempts to focus on the recent research efforts related to spectrum sensing, sharing and allocation, cost-effective architectures, transmission parameter adaptation, energy efficient proposals and security provisioning problems for CR-IoT. Some design issues in CR-IoT system are also being discussed in this chapter.