  We explicitly describe infintesimal deformations of cyclic quotient
singularities that satisfy one of the deformation conditions introduced by
Wahl, Koll\'ar-Shepherd-Barron and Viehweg. The conclusion is that in many
cases these three notions are different from each other. In particular, we see
that while the KSB and the Viehweg versions of the moduli space of surfaces of
general type have the same underlying reduced subscheme, their infinitesimal
structures are different.
