Delayed sleep phase syndrome (DSPS) is a circadian rhythm sleep disorder where the sleep-wake rhythm is significantly delayed according to the environmental demands. Hence, the symptoms consist of major difficulties falling asleep and problems awakening in due time and patients often experience work- and school related impairments (The International Classification of Sleep Disorders: Diagnostic and Coding manual, 2005). However, correct diagnosis is often not made and the treatment offered is, accordingly, often inadequate. DSPS normally develops in interplay between dysfunctional habits/behaviour and biological vulnerability.