We study phase separation in a polymerizing system by means of Monte Carlo simulation on a triangular lattice. This serves as a model for the processes occurring in the formation of polymer-dispersed liquid crystals (PDLCs). The resulting structures are dependent not only on temperature and concentration but also on the relative rates of polymerization and diffusion. The effective phase diagrams observed in the simulations can be approximated by Flory-Huggins theory when the degree of polymerization is treated as an adjustable parameter. The time-resolved structure factor is less well approximated by an expression of the Lifshitz-Slyozov type.