Theoretical calculations using proximity based potentials are performed to pre- dict the fusion cross sections of the reactions of weakly bound projectiles especially halo nuclei with 209 Bi target. Both neutron halo as well as proton halo projectiles are taken in the present analysis. In particular, we study the role of extended nuclear radii of these weakly bound nuclei on the fusion cross sections. The inability of 8 B+ 58 Ni reaction to follow the systematics at above barrier energies motivates us to investigate the trend for the reactions of those weakly bound nuclei for which experiments are not yet performed. Our results indicate that extended radii of these weakly bound nuclei significantly affect fusion barrier heights as well as fusion probabilities throughout the energy range. We also study the fusion probabilities of a few reactions involving tightly bound projectiles.