  We compute the energy levels of a 2D Hydrogen atom when a constant magnetic
field is applied. With the help of a mixed-basis variational method and a
genera lization of virial theorem, which consists in scaling the wave function,
we calculate the binding energies of the 1S, $2P^-$ and $3D^-$ levels. We
compare the computed energy spectra with those obtained via a generalization of
the mesh point technique as well as the shifted 1/N method. We show that the
variational solutions present a very good behavior in the weak and strong
magnetic field regimes.
