More than 100,00 people will be notified from today that their data was compromised in the HSE ransomware attack last May.
Those affected will receive a letter between now and April 2023.
The Health Service Executive's Chief Information Officer, Fran Thompson, explained that Gardaí managed to secure the data targeted by the hackers and return it to the HSE.
They then worked to verify the information and identify those impacted.
Some 113,000 people will receive a letter from the HSE between now and April of next year.
84% of the data was that of patients, while 16% of it related to staff.
A sign for the Health Service Executive (HSE) is seen in Dundalk, Co Louth in 2014. Picture by: Stephen Barnes/Medical / Alamy Stock PhotoIt is a mix of personal, medical, employee and limited financial information.
No compensation is being offered to those affected by the HSE cyberattack.
The HSE has said there is no evidence that the data was used on the internet, and therefore no financial compensation will be offered.
No action is required by those affected, but a call centre has been set up to deal with any queries.
The HSE said last December that it would contact all those affected by the cyberattack, after it was given a copy of the stolen data.
The Garda National Cyber Crime Bureau got this data from the US Department of Justice under a Mutual Legal Assistance Treaty (MLAT), which was processed by the US courts.
A High Court order has been in place since last May to stop all stolen data - including personal and medical information - that may have been taken from being published online.
Additional reporting: Jack Quann
