Proponents of psychiatric rehabilitation believe that active patient participation in rehabilitation planning is essential. Participation assumes, however, that severely mentally ill patients can reliably report their needs. Unfortunately, reliably responding to a needs assessment may be diminished by cognitive deficits that are associated with psychosis and low intelligence. To address this issue, 35 severely mentally ill outpatients completed the Needs and Resources Assessment twice, with 1 week intervening. Their reliability on this task was compared with that of 16 control subjects. Results showed that subjects in both groups performed more reliably (measured as raw agreement) on the more highly structured, standardized items. Patients were less reliable than controls on individualized and standardized items. Further analyses suggested that the patients' raw agreement was found to be significantly associated with thought disturbance. Assessment methods must be sufficiently structured to help cognitively disordered patients provide reliable information for rehabilitation planning.