Some 100,000 patients have been treated since the National Treatment Purchase Fund (NTPF) was created in 2002, according to Minister for Health Mary Harney.
Speaking at an event to mark the milestone, Ms Harney said average waiting times for selected procedures had fallen from up to five years to two to five months.
"The fund is an example of how innovation in the public sector and a targeted solution can be applied to a specific problem with real and measurable results," Ms Harney said.
The NTPF was created in 2002 by then minister for health Micheál Martin to address waiting lists at public hospitals. Patients waiting more than three months for an operation or procedure can apply to have the fund pay for them to get free treatment privately in Ireland or abroad.
The fund is due to provide treatment for over 37,000 patients this year compared to 1,920 in its first year.
Figures published today show the most treatments were provide for were: ophthalmology (13,005); ear, nose and throat (12,524); and general surgery (11,807).
NTPF chief executive Pat O'Byrne said: "Five years ago, the concept of 100,000 patients treated was not even something we ever considered."
The NTPF boosted in services in 2005 through the creation of the online Patient Treatment Register providing information on waiting times in the public health system
It also began providing consultant out-patient appointments for people who had been waiting years to see a consultant. To date, 50,000 patients have been offered appointments.