  We examine the paper basic equations of T. Doma\'nski and K.I. Wysoki\'nski
[Phys. Rev. B {\bf 59}, 173 (1999)], who calculated the critical
superconducting temperature, T_c, in function of Coulomb correlations (U) for
s- and d-wave order parameter symmetries. We give physical arguments, based on
general theory of perturbation, that in their gap equation the Coulomb
repulsion is counted twice. Because of that, we write down the right mean-field
gap equation and solve it by using a normal state one-particle Green function
which gives a Mott metal-insulator transition for $T > T_c$ and which is valid
for any value of U. In consequence, we are not allowed to use mean-field theory
for both U and pairing (V). Our numerical results for T_c vs U shows that U is
detrimental to superconductivity which agrees with the numerical results of
Doma\'nski and Wysoki\'nski. Our results can be extended to any value of the
pairing interaction if superconducting pairing fluctuations are taken into
account.
