This paper studies network selection issues in cooperative cognitive radio networks (CRNs) where secondary users (SUs) have access to the combined spectrum pool of cooperating CRNs. Motivated by the service degradation of SUs caused by unnecessary network handover in cooperative CRNs, we formulate the network selection problem as a nonlinear optimization problem to minimize overall SU handover probability. We subsequently propose three network selection schemes and theoretically evaluate their performance using corresponding Markov chain models. Our numerical results indicate that a jointly-optimized network selection scheme which takes into account both the number of free channels and the traffic intensity of primary users in each CRN obtains the lowest probability of SU handover. Furthermore, compared to the random selection scheme, the jointly-optimized network selection scheme achieves significant reduction in SU handover probability while having no negative impact on other performance metrics of secondary users, such as blocking probability, forced termination probability and completion probability.