  We study two-loop quantum corrections to the low-energy effective actions in
N=(2,2) and N=(4,4) SQED in the Coulomb branch. In the latter model, the
low-energy effective action is described by a generalized Kahler potential
which depends on both chiral and twisted chiral superfields. We demonstrate
that this generalized Kahler potential is one-loop exact and corresponds to the
N=(4,4) sigma-model with torsion presented by Rocek, Schoutens and Sevrin. In
the N=(2,2) SQED, the effective Kahler potential is not protected against
higher-loop quantum corrections. The two-loop quantum corrections to this
potential and the corresponding sigma-model metric are explicitly found.
