We investigated the association between cerebral morphology as revealed by computed tomography and sleep polysomnographic findings in patients with functional psychoses. The third ventricle-brain ratios, caudate ratios, and anterior horn ratios were significantly negatively associated with sleep maintenance and were positively correlated with rapid eye movement (REM) latency. When the effects of illness severity were covaried out, the relation between REM latency and anterior horn ratios remained significant. Disturbances in sleep in some patients with schizophrenia and schizoaffective disorders may be related to dysfunction of forebrain structures, and may be similar to those seen in dementia.