  We study the effect of supersymmetric contributions to the effective quark
transition $b\to s\gamma\gamma$, including leading order QCD effects. We apply
the discussion to the decay $B_s\to\gamma\gamma$. Even though one-particle
irreducible contributions could play a role, numerical cancelations make the
amplitude for the two-photon emission strongly correlated to the $b\to s\gamma$
amplitude which is sharply constrained by experiment. A quite general statement
follows: as long as non-standard physics effects appear only in the matching of
the Wilson coefficients of the standard effective operator basis, the
deviations from the standard model expectations of the decay rates induced by
$b\to s\gamma\gamma$ are bound to follow closely the corresponding deviations
on $b\to s\gamma$. Effects of new physics are therefore bound to be small.
