μ→eγin Theories with Dirac and Majorana Neutrino-Mass Terms

The $\mu \to e\gamma$ decay as induced by massive neutrino mixings is studied. In models with either pure Dirac or Majorana mass terms it is suppressed by small neutrino masses. When both Dirac and Majorana terms are present, one can avoid this mass suppression and the Glashow-Iliopoulos-Maiani cancellation is generally not complete. Then it is suppressed by small mixing angles. However, one instance is found where both suppression mechanisms can be avoided, yielding a "large" $\mu \to e\gamma$ rate.