The traditional diagnosis of patients with disorders of consciousness relies solely on behavioral responses. In 1996 it was estimated that 43% of patients diagnosed with unresponsive wakefulness syndrome (vegetative state) receive the wrong diagnosis. Assessing consciousness is perhaps the most crucial part of the diagnostic process. The challenging task of identifying covert consciousness in this patient group seems to be the biggest issue. In 2006 willful modulation of brain activity in response to a mental imagery task was discovered in a patient with unresponsive wakefulness syndrome. The brain activity was measured with functional magnetic resonance imaging. It was concluded that consciousness was preserved in this patient and new research investigating this novel method began to take place. The aim of this thesis was to conduct a systematic review of the literature and thereby arrive at the best current estimate of the proportion of patients who receive a diagnosis that wrongfully defines them as “unconscious” although they in fact are “covertly conscious”. In this review, 11 studies were examined. The results showed that patients with unresponsive wakefulness syndrome, who still receive the wrong diagnosis, decreased to 22-28% by the use of neuroimaging. This improvement points to the possible use of neuroimaging methods in the diagnosis of disorders of consciousness. However, this result cannot be taken without reservations. The limitations of the studies have to be taken into consideration. For example, most studies included a limited sample size and healthy controls did not always give the expected response to mental imagery tasks.