It is a neglected psychopathological fact that Schneider clearly differentiated the delusional notion linked to a perception (‘wahrnehmungsgebundener Wahneinfall’) from the delusional perception (‘Wahnwahrnehmung’). When this distinction is not taken into account, it is very likely that the probability of a false positive rating for the delusional perception is increased. A possible practical aid to help operationalize the differential ‘diagnosis’ between these two symptoms is offered. The section on ‘delusional’ phenomena in Wing’s present-state examination is then discussed in the light of these distinctions.