Stereoscopy is widely used to render depth and perceptual spatial cues information in Virtual Environments (VEs). In literature, the use of stereoscopy in VEs reported advantages but also disadvantages on perceptual skills such as metric evaluation of distances. The present study tests the influence of stereoscopy on a verbal metric and nonmetric evaluation of egocentric and allocentric distances task, in closed and open scenarios, correlating performance with Mental Rotation ability. Results show that stereoscopy could be helpful only for nonmetric estimates. More errors occurred in metric evaluation, modulated by gender.