This paper studies the dynamic discovery of reliable paths by smart packets in ad hoc cognitive packet networks with the aim of supporting robust communications and services. The reliability of nodes is characterized by time-dependent probability variables that packets observe as they move to their destinations. A feedback system allows the distribution of network information to be exploited by future routing decisions to improve or maintain the reliability of paths. Reliability conditions are continuously monitored by packets and a signal is sent to the source node to restart a discovery process whenever a potential risk is detected. Finally, a simulation study reports the resulting performance of a wireless network when smart packets have routing goals based on hop count and reliability-based metrics. © 2005 IEEE.