Sleep state misperception (SSM) is the diagnostic term proposed in the International Classification of Sleep Disorders to describe those insomniacs who mislabel their sleep as wakefulness. Although sleep misperception has long been recognized among insomnia patients, it is debatable whether this clinical finding warrants a distinctive diagnosis or simply represents an extreme variation of other, more common forms of insomnia. We present two cases to explore the clinical meaningfulness of SSM. It is concluded that SSM represents a distinctive, albeit rare, sleep disorder. However, refinements in existing diagnostic criteria may be needed to improve the meaningfulness of the SSM diagnosis.