UML is one of the major conceptual modeling tools in Object-Oriented software engineering. However, recently more and more concerns arise from the modeling quality of UML. Among them, limitation of the two-dimensional presentation of its notations is reported to be significant. By bringing in the concepts of Steoropsis (3-D appearance), animation, interaction and immersion, Virtual Reality may improve the UML modeling quality. Specifically, in this paper we analyze the modeling quality of UML by using recent published literature in conceptual modeling. We then recommend the use of Virtual Reality to enhance the modeling quality of UML. Some examples of how Virtual Reality can be used to improve UML modeling quality are given. Finally, we propose a research framework for enhancing the quality of UML conceptual modeling through the use of Virtual Reality.