  We discuss the shape dependence of the finite-size scaling limit in a
strongly anisotropic O(N) model in the large-N limit. We show that scaling is
observed even if an incorrect value for the anisotropy exponent is considered.
However, the related exponents may only be effective ones, differing from the
correct critical exponents of the model. We discuss the implications of our
results for numerical finite-size scaling studies of strongly anisotropic
systems.
