The diamond relay channel, or diamond relay network, is a kind of efficient cooperative network in which the source node cooperates with two neighbors. In this paper, we study the impact on the performance of such a network caused by the relays' position for a general Nakagami-m fading channel, which extends the previous work for a special Rayleigh fading case. In particular, the symmetric scenario for the two relays is investigated but the channel conditions of the two source-relay-destination links may have great difference due to the different values of m for the four Nakagami-m fading channels. We study how to select the position of the two relays and give clear restrictions of their positions based on the requirement of the throughout improvement and network stability. Finally, we show how to find the optimal position to achieve the largest throughput improvement. The numerical results confirm our analysis and the interesting illustrations show much insight on the cooperative neighbor selections. Copyright © 2010 John Wiley & Sons, Ltd.