Average rents for properties advertised on Daft.ie have fallen by almost 12% last year, according to figures out today.
The website says the total number of rental properties on the market doubled during 2008, driving down rents nationwide.
South Co Dublin experienced the largest fall in rents at just over 15%, while south Dublin city, Cork and Limerick all experienced falls of around 10%.
Rents in Galway and Waterford fell by 6% and 4% respectively, while rents outside the main cities were down an average of 8%.