Two types of Monte Carlo simulations were carried out to simulate gelation in a living copolymerization of monovinyl monomer and divinyl cross-linker. The simulated gel points under various conditions were compared to the experimental gel points obtained in series of ATRP reactions and the calculated gel points based on Flory-Stockmayer (FS) theory. The first simulation was based on an off-lattice (OL) model, simplified by ignoring the geometry of macromolecules. The second more complex simulation was based on the dynamic lattice liquid (DLL) model. Both OL model and FS mean-field theory were capable to count on the influence of molar ratios of cross-linker to initiator and initiation rate on the gel points. However, the simulated gel points occurred at much lower monomer conversion, as compared to the experimental results. Furthermore, the solvent dilution, an important parameter to adjust the experimental gel points, had no effect on the gel points in both OL simulation and FS theory. In contrast, the DLL simulation based on a cooperative motion of elements on a lattice successfully predicted the effect of solvent dilution on the gel points. Addition of solvent beads in the DLL system decreased the concentrations of initiator, cross-linker, and monomer and significantly postponed the gel points. A decreasing targeted DP of primary chains, while keeping the molar concentrations of initiator and cross-linker constant, also resulted in a delayed gelation, which was confirmed by the ATRP experiments under similar conditions. These results provide means to understand the dependence of gel points on various parameters and can serve as a basis for the development of more advanced simulation models of the controlled/living copolymerization systems.