As observed by Gombrich [Gombrich, E. H. (1960). "Art and illusion." Oxford: Phaidon Press], we confirm that most people are unaware of the size of their own image on mirrors. Specifically we have documented the knowledge that people have of the size of their own head and of the size of the mirror image of their own head. In addition we have explored naive beliefs about how the size of mirror images changes with distance. The main pattern of findings is consistent with a focus on target distance and a difficulty in factoring the observer's vantage point correctly when people reason about the problem. The issue of information about vantage point is discussed in relation to other literatures.