We searched Medline from 1946 to 2019 for reports exploring differences between PNES and other comparable paroxysmal events using clinical instruments, few of which focused on the differential diagnosis using broad-based questionnaires covering multiple aspects of this condition. The majority investigated single items to highlight specific differences, either qualitative or quantitative, between groups and to elucidate some of the pathogenetic mechanisms of PNES. We selected all variables that proved to be useful for differentiating PNES from other types of paroxysmal events and classified them by category, by instrument utilized and method of investigation. This body of data will constitute the basis for assembling a new set of evidence-based questionnaires for patients and eyewitnesses to facilitate the differential diagnosis of these disorders, especially in resource-poor clinical settings. This will require a skillful translation of the content of each selected variable into clear and intuitive questions, appropriate for lay responders. Predictive variables found by more than one investigator, especially if using different approaches, have greater diagnostic weight and should be prominent in future questionnaires. However, even variables so far found to be predictive by one investigator will deserve consideration. Once the preliminary text of the questionnaires is consolidated, the instrument will need extensive testing and validation in large prospective studies before becoming available for clinical use in its definitive format.