  We analyse late-time observations, available photometry and spectra, of a
sample of type II plateau supernovae (SNe IIP). The possibility of using
H$\alpha$ luminosity at the nebular epoch as a tracer of $^{56}$Ni mass in this
class of objects is investigated, yielding a consistency with the
photometry-based estimates within 20%. Interesting correlations are found and
their impacts on our present understanding of the physics of core collapse SNe
are discussed.
