  We present a scheme for the generation of central exclusive final states in
the Pythia 8 program. The implementation allows for the investigation of higher
order corrections to such exclusive processes as approximated by the
initial-state parton shower in Pythia 8. To achieve this, the spin and colour
decomposition of the initial-state shower has been worked out, in order to
determine the probability that a partonic state generated from an inclusive
sub-process followed by a series of initial-state parton splittings can be
considered as an approximation of an exclusive colour- and spin-singlet
process. We use our implementation to investigate effects of parton showers on
some examples of central exclusive processes, and find sizeable effects on
di-jet production, while the effects on e.g. central exclusive Higgs production
are minor.
