A similarity solution is presented to study the influence of lateral mass flux and thermal dispersion on non-Darcy natural convection over a vertical hat plate with an exponential type of internal heat generation in a fluid saturated porous medium. The coefficient of thermal diffusivity has been assumed to be the sum of molecular diffusivity and the dispersion thermal diffusivity due to mechanical dispersion. The suction/injection velocity distribution has been assumed to have power function form Ax(lambda), where x is the distance from the leading edge and the wall temperature distribution is assumed to be uniform.