This paper proposes a combination of virtual reality (VR) and constraint programming (CP) to develop an efficient system that will assist users when performing 3D layout tasks in a virtual environment. We conducted an experimental study to investigate the extent to which the solver’s assistance affects user performance in 3D-layout tasks. Volunteer participants were instructed to layout a generic 3D scene which was displayed on a large-scale rear-projected screen. Results showed that the solver provided significant assistance in both simple and complex tasks. The participants performed the layout tasks more accurately and in significantly less time when the constraint solver was used. Most of the subjects reported that the solver was useful in completing the layout tasks and they were generally satisfied by the proposed solution. However, it was observed that some subjects had difficulty in interacting with the solver, especially during the complex tasks.