CIA aircraft landed at Shannon airport in the south-west of Ireland on 38 occasions in recent years, Irish state radio said Monday, quoting government data.
RTE said it had received the data about the flights from the government under freedom of information laws.
Last week, Foreign Minister Dermot Ahern said after talks in Washington with US Secretary of State Condoleezza Rice that he accepted her assurances that Shannon had not been used for "anything untoward".
Shannon, the first airport across the North Atlantic from the United State, is an increasingly important re-fuelling stop for US military planes.
Some 268,963 US military personnel passed through Shannon airport in 2005 up to the end of October, compared to 158,549 in the whole of 2004.
There is mounting concern over reports the CIA ran secret prisons in Eastern Europe and used European airports for clandestine transport flights when transferring terror suspects in a process known as "rendition".