OBJECTIVE - To provide an update on recent research on depression and anxiety in obstructive sleep apnea syndrome (OSAS). METHODS - A review was carried out on reports drawn from MEDLINE and PSYCHLIT (January 1995-June 2006) and identified from their list of references. The selection criteria were met by 55 articles. RESULTS - Sample sizes in the reviewed studies varied widely and consisted mainly of working age men. Depression and anxiety were mostly evaluated with commonly used mood scales; only a few studies provided a psychiatric diagnosis. Prevalence figures fluctuated considerably for both depression (7-63%) and anxiety (11-70%). The effect of the continuous positive airway pressure (CPAP) on mood was inconsistent. CONCLUSIONS - Variations in the prevalence of depression and anxiety are affected by patient characteristics, mood assessment methods, and overlap between mood alterations and OSAS-related symptoms. CPAP might improve mood alterations but more long-term follow-up studies are needed to verify the effectiveness.