Any face seen for the first time will have a closet neighbour in memory. In order to avoid false alarms, we must be able to distinguish similar from identical faces. Work is reported investigating same/different judgments as a function difference in three dimensional shape defined in terms of standard deviation in a principal component based face space. The aim is to determine the criterion difference below which observers respond “same”. A threshold corresponding to a dprime of 1 was also calculated. Both were first measured under three conditions – same view images, different view images and animated images of the faces rotating. Criterion did not differ significantly between presentation conditions and the mean criterion corresponded to 0.45 SD when the average face was used as the reference. Threshold did differ significantly between conditions, and was significantly higher for different view faces (.65SD) than for same view (.39SD) or animated faces (.44SD). The results are interpreted as indicating that the criterion for same/different judgements is relatively stable across presentation conditions, but that sensitivity is lower when making the judgement across a change in view. Further work will investigate whether criterion varies as a function of distinctiveness.