Conducted 3 experiments using a total of 283 male and female high school students. Exp I demonstrated that the more desirable the self-rating on a personality characteristic, the more central that characteristic is in perceiving others. This self-image bias in person perception was hypothesized to reflect the defense mechanism protecting high self-evaluation. In Exp II it appeared that, consistent with this defense interpretation, there was lower self-image bias among Ss in a condition that reduced defensiveness by using objective self-awareness techniques. Exp II also suggested an alternative to this defense explanation: a purely cognitive process whereby self-image mediates external evaluative stimuli and centrality of characteristics. Exp III attempted to test this alternative explanation; results support a cognitive interpretation of self-image bias in person perception.