The extensive utilization of wireless sensor networks (WSNs) in SHM systems promotes optimal wireless sensor placement (OWSP) as an important topic. In this paper, the theoretical framework of OWSP in SHM is presented. Within the framework, the energy-aware wireless sensor placement is formulated as a discrete optimization problem in which the linear independence of identified mode shapes is achieved, the connectivity of the WSN is guaranteed, and the energy efficiency of an entire WSN is pursued. A hybrid discrete firefly algorithm (HDFA) is developed to solve this complex optimization problem. The one-dimensional binary coding system and the Hamming distance are adopted to characterize the fireflies so that the distinguished optimization mechanism in the basic FA can be applied to the OWSP problem. A hybrid movement scheme including directive movement and nondirective movement is proposed to improve the convergence speed, enhance the capability of searching global optimization, and avoid falling into the local optimum. The HDFA is applied to a long-span suspension bridge for verifications, and two other optimization methods, a simple discrete FA and a simple genetic algorithm, are also employed for facilitating comparisons. The results demonstrate that the HDFA can extract an optimal wireless sensor configuration with highly linear independence of identified mode shapes and outstanding WSN performance. And the combination of directive movement and nondirective movement proves that the HDFA can outperform the simple discrete FA and the simple genetic algorithm in terms of computational efficiency and superiority of results. Copyright (c) 2014 John Wiley & Sons, Ltd.