  We consider the three basic seesaw scenarios (with fermionic singlets, scalar
triplets or fermionic triplets) and discuss their phenomenology, aside from
neutrino masses. We use the effective field theory approach and compare the
dimension-six operators characteristic of these models. We discuss the
possibility of having large dimension-six operators and small dimension-five
(small neutrino masses) without any fine-tuning, if the lepton number is
violated at a low energy scale. Finally, we discuss some peculiarities of the
phenomenology of the fermionic triplet seesaw model.
