  Astrophysical and cosmological observations do not require the dark matter
particles to be absolutely stable. If they are indeed unstable, their decay
into positrons might occur at a sufficiently large rate to allow the indirect
detection of dark matter through an anomalous contribution to the cosmic
positron flux. In this paper we discuss the implications of the excess in the
positron fraction recently reported by the PAMELA collaboration for the
scenario of decaying dark matter. To this end, we have performed a
model-independent analysis of possible signatures by studying various decay
channels in the case of both a fermionic and a scalar dark matter particle. We
find that the steep rise in the positron fraction measured by PAMELA at
energies larger than 10 GeV can naturally be accommodated in several
realizations of the decaying dark matter scenario.
