  We investigate the behavior of semi-orthogonal decompositions of bounded
derived categories of singular varieties under flat deformations to smooth
varieties. We consider a Q-Gorenstein smoothing of a surface with a quotient
singularity, and prove that a pretilting sheaf, which is constructed from a
non-commutative deformation of a divisorial sheaf and generates a
semi-orthogonal component of a bounded derived category, deforms to a direct
sum of exceptional vector bundles which are mutually totally orthogonal.
