Rents across the country rose by 7.1% in the second quarter of this year.
The increase was larger in Dublin, with rent prices rising by 9.2% compared to 5.8% in the rest of the country.
The rent for houses outside Dublin increased by 5.8%, while apartments outside Dublin experienced an increase of 5.9%.
The average monthly rent in Dublin is over €1,300 while outside the capital it is almost half that - at €677 a month.
The rent for apartments nationally was €922 (€857 a year earlier) and for a house it was €853 (€801 a year earlier).
In Dublin, the rent in 2015 was €1,387 for a house and €1,260 for an apartment. A year earlier, the rent for a house was €1,275, and for an apartment it was €1,152.
This represents a monthly increase in Dublin rent of €112 for a house and €108 for an apartment over the course of the 12 month period.
It comes days after another study showed that in the majority of places around the country, mortgage repayments have become cheaper than monthly rent.
David Duffy is an economist with the ESRI. He told Newstalk Breakfast growth rates can vary depending on where you are.
Anne-Marie Caulfield from the Private Residential Tenancies Board (PRTB) says that there are a number of reasons rents are on the rise.