  We make a detailed study of the effect that the recently predicted
modification of the in-medium masses of charmed mesons would have on $J/\Psi$
dissociation on pion and $\rho$-meson comovers in relativistic heavy ion
collisions. We find a substantial dependence of the $J/\Psi$ absorption rates
on the density and temperature of the nuclear matter. This suggests that a
quantitative analysis of $J/\Psi$ dissociation in nucleus nucleus collisions
should include the effects of the modification of meson masses in dense matter.
