  We discuss the statistical properties of lifetimes of electromagnetic
eigenmodes in dielectric microresonators with fully chaotic ray dynamics. Using
the example of a resonator of stadium geometry, we find that a recently
proposed random-matrix model very well describes the lifetime statistics of
long-lived resonances, provided that two effective parameters are appropriately
renormalized. This renormalization is linked to the formation of anomalously
short-lived resonances, a mechanism also known from the fractal Weyl law and
the resonance trapping phenomenon.
