We present a study of the transmission coefficients of two-dimensional photonic band gap materials consisting of dielectric cylinders in graphite arrangement. By the study of the attenuation versus slab thickness, we determine the most efficient graphite configuration. We show how uncoupled modes create opaque regions for plane waves propagating along the &Ggr;-P direction and widen the gap originating from the existence of forbidden photonic bands. Our results demonstrate that graphite structure is a promising geometry yielding an attenuation as strong as triangular structure with greater convenience in the fabrication at the submicronic scale. ©1997 American Institute of Physics.