The widely used cross-correlation technique for leak detection requires that the leakage acoustic vibrations propagate along the gas pipelines over a significant distance as a single non-dispersive mode at a fixed velocity. In practice, the acoustic vibrations propagate along multiple paths including in-pipe gas and pipe wall, and the ones in different transmission paths possess different modal distributions and different dispersive behaviors, which bring a great challenge for leak detection in the gas pipelines. In this work, a modal extraction scheme is proposed by determination of dominant transmission path and vibration pick-up direction for improving leak detection in gas pipelines. Based on the vibration theory of cylindrical thin shell, the acoustical coupling between the in-pipe gas and the pipe wall is analyzed to determine a dominant transmission path. Then, the dispersive characteristics and modal distributions of acoustic vibrations at different directions in the dominant transmission path are analyzed using guided wave theory. Finally, the experimental investigations convince theoretical analyses and demonstrate that the axial vibrations in dominant transmission path are dominated by a single non-dispersive mode with high signal-to-noise ratio (SNR) in the frequency region 0-2.5 kHz. The findings provide useful leads for improving leak detection in the gas pipelines. (C) 2016 Elsevier Ltd. All rights reserved.