There is significant interest in novel accelerating techniques which can overcome the limitations of conventional radio-frequency (RF) based devices in terms of frequency, gradient, and footprint. Moving from the RF to the terahertz (THz) frequency range, higher accelerating-gradient of high-energy beams can be achieved, as well as structure miniaturisation. Fur-thermore, in respect to the optical frequency range, THz allows for larger structures and better beam quali-ty. This work has been investigating the use of a 2D photonic-bandgap dielectric waveguide (PBG-W) for THz-driven electron acceleration which could poten-tially offer a good compromise between dispersion engineering, low losses and ease of parallel illumina-tion. Dispersion characteristics of the accelerating mode are studied to achieve the best compromise be-tween high accelerating field and effective accelerat-ing bandwidth, assuming a ~10% bandwidth of the THz driving pulse.