People with an acquired brain injury can wait up to two years for access to the National Rehabilitation Hospital in Dún Laoghaire, according to figures obtained by RTÉ News.
An estimated 30,000 people in Ireland are currently living with a brain injury.
Health Service Executive figures show there are 13 people with acquired brain injuries who have been waiting between one and two years for admission to the NRH.
A further 22 people have been waiting between six months and a year.
In a statement, the HSE confirmed there are just three beds available in the hospital for patients with complex or severe brain injuries.
Acquired Brain Injury Ireland says rising waiting lists and a shortage of beds in the NRH is having a major impact.
The charity also says there is a lack of community-based care for people who have been discharged from rehab.