Cognitive dysfunction and depression are the most frequent psychiatric problems in the elderly population. However, it is difficult to assess the status of sleep disorder as well as depression among patients with cognitive dysfunction based on self-reported symptoms. The purpose of this study was to elucidate the relationship between sleep-wake patterns and depression among institute-dwelling elderly with cognitive dysfunction. The subjects were 39 elderly patients (age 84.1±8.7, HDS-R 8.6±6.2, Barthel Index 43.2±30.3) in a convalescent hospital. The Cornell Scale for Depression in Dementia (CSDD) was used to assess the status of depression of the elderly with cognitive dysfunction. Their 59-day sleep-wake patterns were monitored and recorded in the sleep log by nurses. The total sleep time (r=-0.423, p=0.007), the longest sleep episode at nighttime (r=-0.360, p=0.024), and intermittent awakening time at nighttime (r=0.329, p=0.041) were associated with depression. These results suggest a close relationship between depression and difficulty in sleep maintenance among the elderly with cognitive dysfunction as well as among the general population, and also that CSDD can be an efficient tool for the assessment of their depressive status. If this is true, it is important in making care plans for sleep disorders among elder patients with cognitive dysfunction to take into account the effects of depression on sleep-wake patterns.