Background. People with persecutory delusions regard ambiguous data in the social domain as self-relevant and selectively attend to threatening information. This study aimed to characterize these social cognitive biases in functional neuroanatomical terms. Method. Eight schizophrenic patients with active persecutory delusions and eight matched normal controls underwent functional magnetic resonance imaging while determining the self-relevance of ambiguous self-relevant or unambiguous other-relevant neutral and threatening statements. Results. In determining self-relevance, the deluded subjects showed a marked absence of rostral-ventral anterior cingulate activation together with increased posterior cingulate gyrus activation in comparison to the normal subjects. The influence of threat on self-relevance determination did not yield statistically significant differences between deluded and normal subjects. Conclusions. Abnormalities of cingulate gyrus activation while determining self-relevance suggest impaired self-reflection in the persecutory deluded state. This may contribute to persecutory belief formation and maintenance.