  We consider gravitational scattering of point particles with Planckian
centre-of-mass energy and fixed low momentum transfers in the framework of
general relativity and dilaton gravity. The geometry around the particles are
modelled by arbitrary black hole metrics of general relativity to calculate the
scattering amplitudes. However, for dilaton gravity, this modelling can be done
{\it only} by extremal black hole metrics. This is consistent with the
conjecture that extremal black holes are elementary particles.
