The population of people with congenital deafblindness faces challenges concerning communication and mobility. Due to the significance of the sensory loss it is difficult to diagnose mental and behavioral disorders. This article investigates the prevalence of mental and behavioral disorders among 95 congenitally deafblind adults. Seventy-four percent were found to have a mental and/or behavioral diagnose. Mental retardation was found among 34%, psychosis among 13%. Mental and behavioral disorders, especially with symptoms of psychosis and mental retardation, are common among people with congenital deafblindness. Clinical experience is needed, as well as cross-disciplinary cooperation and specialized diagnostic methods together with a observation and intervention period in order to be able to assess and differentiate mental and behavioral symptoms from sensory deprivation in people with congenital deafblindness. (Contains 1 table.)