  Weak decays in superheavy nuclei with proton numbers Z = 118 - 120 and
neutron numbers N = 175 - 184 are studied within a microscopic formalism based
on deformed self-consistent Skyrme Hartree-Fock mean-field calculations with
pairing correlations. The half-lives of beta+ decay and electron capture are
compared with alpha-decay half-lives obtained from phenomenological formulas.
The sensitivity of the half-lives to the unknown Q-energies is studied by
comparing the results obtained from different approaches for the masses. It is
shown that alpha-decay is always dominant in this mass region. The competition
between alpha and beta+/EC decay modes is studied in seven alpha-decay chains
starting at different isotopes of Z=118, 119, and 120.
