Mood disorders and sleep disturbances are closely related. In elderly people, the prevalence of insomnia and depressive symptoms is increased. Moreover, somatic co-morbidities associated with aging are known to be risk factors for both insomnia and depression. Assessment of the origin of sleep complaints must consider primary and secondary insomnia, and the existence of associated depression. Causal treatment of insomnia is necessary keeping in consideration that depressive dimension can, afterward, evolve on its own. In presence of intense sleep complaints in inadequacy with somatic examination, and not documented by sleep recordings, depression must be evoked. In patients with a diagnosis of depression, treatment and monitoring of the evolution of insomnia is necessary, because persistent disturbances of sleep are associated with poor prognosis. Concerning the therapeutics, beyond antidepressant treatment and psychotherapy, chronotherapy is a promising, but still not yet evaluated, approach, which presents the advantage to limit the use of psychotropics drugs.