This paper examines the problems of applying traditional function points count rules to virtual reality systems (VRS). From the analysis of the differences between traditional and VRS systems, a set of deficiencies in the IFPUG 4.1 function points count method was detected. Due to the increasing importance of these kinds of applications, it is necessary to study how traditional function points count rules can be adapted to estimate VRS. In this paper, we are going to focus on the possibility of estimating function points accurately using a proposed guideline which was successfully applied to estimate two VRS.