  We point out that leptonic weak-basis invariants are an important tool for
the study of the properties of lepton flavour models. In particular, we show
that appropriately chosen invariants can give a clear indication of whether a
particular lepton flavour model favours normal or inverted hierarchy for
neutrino masses and what is the octant of $\theta_{23}$. These invariants can
be evaluated in any conveniently chosen weak-basis and can also be expressed in
terms of neutrino masses, charged lepton masses, mixing angles and CP violation
phases.
