Objective: There is little systematic evidence to determine if patients with thought disorder are aware of their impaired communication. Awareness versus unawareness of deficit has important implications for neurocognitive models of thought disorder, The aims of this study were to assess awareness of impaired communication in patients prone to thought disorder, and to explore associations between degree of awareness of thought disorder, objective measurement of thought disorder and performance on tests sensitive to impaired executive ability. Method: Thirty-one patients with schizophrenia, 16 patients with mania and 20 well controls were included. Subjects completed a new instrument to assess awareness of thought disorder, the Communication Awareness Scale (CAS). Thought disorder was rated from free speech samples scored with Andreasen's Scale for the Assessment of Thought Language and Communication. Four tests sensitive to impaired executive ability were administered. Results: Subjects with higher levels of positive thought disorder had significantly higher CAS scores. Unexpectedly, those with lower scores on executive ability had significantly higher scores on the GAS. Conclusions: The significant correlation between objective levels of positive thought disorder and higher scores on the CAS suggests that, overall, patients with thought disorder are aware of their deficit. A neurocognitive model of thought disorder is described that involves a dissociation between the ability to monitor errors (required for accurate awareness of deficit) and the ability to correct errors (required for the production of efficient communication).