The goal of this study was to test the effectiveness of stereoscopic compared to 2D standard displays of luggage X-Ray images. Two different participated in the study - expert luggage screeners and inexperienced students. The inexperienced participants yielded no differences in performance between the stereoscopic display and the 2D stansard display in of the measures tested. Their performance was equally poor using both displays. For the expert luggage screeners, a significant difference was found between these two displays. Detection and identification rates were significantly higher for the stereoscopic display than for the 2D standard display. However, the false alarm rate was also higher for the stereoscopic display than the 2D standard display. The subjective feedback given by these participants indicated that most of the experts were satisfied with the stereoscopic display and only one complainedof certain physical discomfort. In contrast, the inexperienced participants had many complaints. It was concluded that stereoscopic display affects the performance of expert luggage screeners by changing their decision criterion, which increases their tendency to mark targets (whether correctly or incorrectly). The importance of increasing the likelihood of detecting suspicious objects is crucial for public safety, but one cannot ignore the fact that many false alarms would result in unnecessary luggage inspection, and concequently, longer queues and higher costs.