Only a fraction of patients in coma secondary to a primary acute brain injury develop a vegetative state (VS). At least 20% of patients show late transitions to a minimally conscious states (MCS). They are particularly common in young adults with traumatic brain injury. The main problems faced by clinicians are the diagnostic accuracy of VS and MCS as well as the usefulness of sophisticated paraclinical investigations. Specific therapies are of limited effectiveness. This population is vulnerable to misdiagnosis and limited access to medical care and rehabilitation, thus generating ethical problems.