This paper presents the results of experimental studies that were undertaken to test the impacts of Virtual Reality (VR) on Discrete-Event Simulation (DES). The experiments focused on spotting errors in the DES model. The models were developed in 2D and 3D/VR displays using WITNESS. The 2D display used icons and other visualization techniques that confine its scope to essentially flat 2D surface. On the other hand, the 3D display was represented by means of a three-axis spatial position (XYZ) plots, but appeared on a two-dimensionally mappings, otherwise known as 2.5D. The experiments involved paid participants who were recruited from amongst the staff and students of Lancaster University, UK. The results showed that it is easier, and faster to spot errors in 3D/VR model than in 2D. The findings also indicated that users can easily understand the modeled operation of 3D/VR display compared to 2D, irrespective of background or technical ability.