  We study the influence of the scheme for the correction for spurious
center-of-mass motion on the fit of effective interactions for self-consistent
nuclear mean-field calculations. We find that interactions with very simple
center-of-mass correction have significantly larger surface coefficients than
interactions for which the center-of-mass correction was calculated for the
actual many-body state during the fit. The reason for that is that the
effective interaction has to counteract the wrong trends with nucleon number of
all simplified schemes for center-of-mass correction which puts a wrong trend
with mass number into the effective interaction itself. The effect becomes
clearly visible when looking at the deformation energy of largely deformed
systems, e.g. superdeformed states or fission barriers of heavy nuclei.
