This is a continuation of our paper [2]. We prove that for functions f in the Hölder class Λ α (R) and 1 < p < ∞, the operator f (A) − f (B) belongs to S p/α , whenever A and B are self-adjoint operators with A − B ∈ S p . We also obtain sharp estimates for the Schatten-von Neumann norms f (A) − f (B) S p/α in terms of A − B S p and establish similar results for other operator ideals. We also estimate Schattenvon Neumann norms of higher order differences m j =0 (−1) m−j m j f (A + jK). We prove that analogous results hold for functions on the unit circle and unitary operators and for analytic functions in the unit disk and contractions. Then we find necessary conditions on f for f (A) − f (B) to belong to S q under the assumption that A − B ∈ S p . We also obtain Schatten-von Neumann estimates for quasicommutators f (A)R − Rf (B), and introduce a spectral shift function and find a trace formula for operators of the form f (A − K) − 2f (A) + f (A + K).