Abstract- Ad-hoc routing protocols with cognitive capabilities have been proposed which solves the problem of spectrum scarcity. It does it by intelligently allowing the unlicensed devices to opportunistically communicate in the available licensed spectrum, while ensuring that the performance of the licensed users is not affected. New emerging routing protocols is a taxing job due to variation in channel usage and channel accessibility by nodes in the network. In this paper, we discussed about adaption of On-Demand routing protocols for cognitive scenario by addressing their merits and demerits.