The relationship between sleep architecture and attentional performance was evaluated in neuroleptic-naive patients with schizophrenia and healthy controls. Participants were recorded in a sleep laboratory for two consecutive nights after which selective and sustained attention performance was tested. In both groups of participants, Spearman's rho statistics revealed a negative correlation between reaction time on the selective attention task and sleep spindle density. Only control participants showed a negative correlation between reaction time and duration of stage 2 sleep and a positive correlation between reaction time and duration of stage 1 ("light") sleep. Only persons with schizophrenia showed a negative correlation between reaction time and duration of stage 4 ("deep") sleep. In the sustained attention task, we found no correlation between reaction time and sleep for control participants while persons with schizophrenia showed a negative correlation between reaction time and duration of stage 4 sleep. It is proposed that EEG sleep spindle activity is associated with automatic attentional processing, while stage 2 sleep continuity in healthy individuals and percentage of stage 4 in patients with schizophrenia are associated with voluntary processes. These results support the existence of a relationship between non-rapid-eye-movement sleep and cognitive performance in healthy individuals as well as in persons with schizophrenia.