  Recent detection of the isotope $^7$Be (that decays into $^7$Li) in the
outburst of classical novae confirms the suggestion made in the 70s that novae
could make $^7$Li. We reconsidered the role of novae as producers of Li by
means of a detailed model of the chemical evolution of the Milky Way. We showed
that novae could be the Galactic lithium source accounting for the observed
increase of Li abundances in the thin disk with stellar metallicity. The best
agreement with the upper envelope of the observed Li abundances is obtained for
a delay time of ~ 1 Gyr for the nova production and for an effective Li yield
of $1.8 (\pm 0.6) \times 10^{-5}$ $M_{\odot}$ over the whole nova life. Lithium
in halo stars is depleted by ~ 0.35 dex, assuming the pristine abundance from
standard big bang nucleosynthesis. We elaborate a model that matches the
pristine stellar abundances, assuming that all stars are depleted by 0.35 dex.
In this case, the delay remains the same, but the Li yields are doubled
compared to the previous case. This model also has the merit to match the Li
abundance in meteorites and young TTauri stars. The thick disk model, adopting
the parameters derived for the thin disk, can also explain the absence of
increase of Li abundances in its stars. The thick disk is old, but formed and
evolved in a time shorter than that required by novae to contribute
significantly to Li. Therefore, no Li enhancement is expected in thick disk
stars. We show that the almost constant Li abundance in the thick disk results
from the compensation of stellar astration by spallation processes.
