In this paper, we report the results of lateral self-diffusion studies of selenium in polycrystalline CulnSe(2) thin films using a radioactive tracer scanning technique. The self-diffusion coefficients were determined in the temperature range 200-400 degrees C; a pre-exponential factor of 5.53 x 10(-4) cm(2) s(-1) and an activation energy of 0.26+/-0.02 eV were evaluated. The activation energy is attributed to selenium diffusion via grain boundaries. The grain boundary energy was also estimated and was found to decrease with increase of temperature.