The propagation characteristics of flexural waves in two-dimensional thin-plate phononic crystals (PCs) are analysed with the plane wave expansion (PWE) method to yield phase constant surfaces, which predict high directivity of flexural wave propagation for certain frequencies outside the band gap. The prediction is validated through the computation of the harmonic responses of a finite structure with 9×9 unit cells. The results indicate that directional propagation of flexural waves is an inherent characteristic of two-dimensional thin-plate PCs while specific effects of the directional propagation in a finite structure vary with the positions of excitations.