  We investigate chiral symmetry breaking and strong CP violation effects in
the phase diagram of strongly interacting matter. We demonstrate the effect of
strong CP violating terms on the phase structure at finite temperature and
densities in a 3-flavor Nambu-Jona-Lasinio (NJL) model including the
Kobayashi-Maskawa-t'Hooft (KMT) determinant term. This is investigated using an
explicit structure for the ground state in terms of quark-antiquark condensates
for both in the scalar and the pseudoscalar channels. CP restoring transition
with temperature at zero baryon density is found to be a second order
transition at $\theta = \pi$ while the same at finite chemical potential and
small temperature turns out to be a first order transition. Within the model,
the tri-critical point turns out to be $(T_c,\mu_c)\simeq(273,94)$ MeV at
$\theta = \pi$ for such a transition.
