The HSE will shortly start notifying people whose information was illegally accessed in last year's national data breach.
113,000 people will be contacted by letter in the coming months relating to the cyber-attack in May 2021.
86% of the notifications relate to patient data and 14% to staff data.
The HSE said 94,000 patients and approximately 18,200 members of staff will be contacted.
Everyone affected will be informed by April 2023.
"People being notified will receive a letter telling them what part of their personal information was impacted," said Joe Ryan, HSE National Director.
"The letter will also outline how, if they wish to do so, people can then request to view their exact documents which were illegally accessed and copied, which can be done via a portal on the HSE website,'' explained Mr Ryan.
The HSE said it found no evidence that people's personal data has been shared or used fraudulently.
Those affected will also have the opportunity to seek advice and support from the HSE.
"We expect this process will take a number of months to complete, as we take the time to contact each person; ensure we have a secure communication with them; and go through the process of assisting them if they want to make a request to view their documents," said Mr Ryan.
More than 80% of the HSE's IT infrastructure and health service sites all over the country were affected by the cyber-attack in May 2021.
Tusla and Children's Health Ireland, which shares some systems with the HSE, were also impacted.
The HSE said Tusla is working through a substantial number of records relating to people whose personal information was affected by the cyber-attack and will begin their own notification process to people affected in the coming weeks.
''We will continue to liaise with the Data Protection Commission and to work closely with our technical experts, An Garda Síochána and the National Cyber Security Centre,'' the HSE said in a statement.
The HSE said it regrets that the data breach happened and has apologised to all those affected.
It said its cyber security experts are continuing to monitor the internet and the dark web for illegally accessed information and it will act immediately if they see any evidence of this.
Because the cyber-attack is the focus of an ongoing criminal investigation, it limits the amount of detailed information the HSE can share in the public domain in relation to the data.