Circadian Rhythm Sleep Disorders (CRSD) are a group of sleep disorders characterized by a malsynchronization between a person's biological clock and the environmental 24-h schedule. These disorders can lead to harmful psychological and functional difficulties and are often misdiagnosed and incorrectly treated due to the fact that doctors are unaware of their existence. In the following review we describe the characteristics of CRSD, diagnosis, treatment as well as their relationship to psychopathology, psychotropic drugs and head trauma.