  We study both static and transport properties of model quantum dots,
employing density functional theory as well as (numerically) exact methods. For
the lattice model under consideration the accuracy of the local-density
approximation generally is poor. For weak interaction, however, accurate
results are achieved within the optimized effective potential method, while for
intermediate interaction strengths a method combining the exact diagonalization
of small clusters with density functional theory is very successful. Results
obtained from the latter approach yield very good agreement with density matrix
renormalization group studies, where the full Hamiltonian consisting of the dot
and the attached leads has to be diagonalized. Furthermore we address the
question whether static density functional theory is able to predict the exact
linear conductance through the dot correctly - with, in general, negative
answer.
