In this report the translational self-diffusion behavior of calamitic mesogens in smectic phases measured by means of NMR diffusometry will be reviewed. In particular the results reported demonstrate that translational diffusion in smectic phases is strongly dependent on molecular packing in the layered structure, but, in contrast with previous assertions seems to be only slightly affected by the clinicity of the phases, i.e., supporting the second order character of the phase transition going from the synclinic to the anticlinic structure typical in chiral Smectic C* phases.