  We present a theory for the dissipation of electronic spins trapped in
quantum dots due to their coupling to the host lattice acoustic phonon modes.
Based on the theory of dissipative two level systems for the spin dynamics, we
derive a relation between the spin dissipative bath, the electron confinement,
and the electron-phonon interaction. We find that there is an energy scale,
typically smaller than the electronic lateral confinement energy, which sets
the boundary between different dissipative regimes .
