Video streaming, as a bandwidth-hungry and delay-sensitive application, can be supported with the Cognitive Radio (CR) technology, which is effective in exploiting the underutilized allocated spectrum. In this article, we examine the challenges of quality of experience (QoE) driven video streaming over CR Networks (CRN) and review existing solutions proposed in the literature. We also discuss the unique features in the optimization of QoE-driven video streaming over CRNs. This article is concluded with a discussion of several open problems that call for substantial future research efforts.