In this study, the detection probability for amplify–forward‐based cooperative relay networks, where the destination is equipped with a selection combiner and energy detector, is analysed. The probability density function method and an alternative series representation of the generalized Marcum‐Q function are used to obtain two upper bounds for the average detection probability. The error bounds resulting from truncating an infinite summation series to finite terms are also calculated because the derived expressions were in the form of an infinite summation series. Finally, the analysis are validated by simulations. These results are expected to assist in future studies of communication technologies, such as cognitive radios. Copyright © 2013 John Wiley & Sons, Ltd.