Recent studies have shown that insomnia is linked to increased negative emotions and decreased positive emotions. The aim of this study was to evaluate the efficacy of an internetbased cognitive-behaviour treatment for insomnia (CBT-I) in ameliorating self-reports of emotional states in the evening and in the morning. Until now, 10 patients with insomnia (8F, 2M), diagnosed according to DSM-IV criteria were assigned to either a CBT-I or a waiting-list (WL) group. Self-reports of positive and negative emotional states collected through emotion diaries filled in during the week preceding the treatment and the week following the end of the treatment were compared. Preliminary results showed that the CBT-I group at post-treatment reported reduced negative emotions in the morning both as compared to the WL group and to the pre-treatment. Preliminary results suggest that internet-delivered CBT-I is efficacious in ameliorating daytime symptoms of insomnia as altered emotional states.