  The question of the existence of pre-main sequence (PMS) $\gamma$~Doradus
($\gamma$~Dor) has been raised by the observations of young clusters such as
NGC~884 hosting $\gamma$~Dor members. We have explored the properties of
$\gamma$~Dor type pulsations in a grid of PMS models covering the mass range
$1.2 M_\odot < M_* < 2.5 M_\odot$ and we derive the theoretical instability
strip (IS) for the PMS $\gamma$~Dor pulsators. We explore the possibility of
distinguishing between PMS and MS $\gamma$~Dor by the behaviour of the period
spacing of their high order $gravity$-modes ($g$-modes).
