Diminished quality of life (QoL) has been reported in patients with mood disorders. QoL has also been shown to be decreased by sleep disturbances. Since sleep disorders are common in mood disorders, the aim of this study was to determine whether sleep characteristics are associated to QoL among patients with Bipolar Disorder (BD) and unipolar Major Depressive Disorders (MDD).QoL was assessed in 170 patients with mood disorders (61 BD and 109 MDD), who also completed questionnaires measuring the severity of insomnia, sleepiness, chronotype preference and obstructive sleep apnea (OSA) probability index.Analyses showed that BD and MDD groups had similar QoL and sleep measures but the MDD group had higher OSA scores. In BD, correlations indicated a relationship between QoL and insomnia complaints and sleepiness, whereas in MDD, correlations indicated an association between QoL and insomnia complaints and OSA score. In both groups, QoL was related to depressive symptomatology. Linear regressions showed that, in BD, QoL was related to insomnia complaints and sleepiness even in the euthymic state, whereas in MDD, QoL was related to insomnia complaints but not in euthymic patients.QoL is related to sleep differently in BD and MDD. The results suggest that insomnia and sleepiness are particularly high in BD even when patients are euthymic. These findings suggest that focusing on insomnia and sleepiness during different mood states of BD could increase QoL.