Customs officers have seized 500,000 cigarettes in Rosslare, Co Wexford.
The cigarettes were found during the search of an articulated truck and trailer carrying electrical equipment, which arrived on a ship from Cherbourg in France.
The illegal haul was found in a specially-constructed, concealed compartment in the floor of the trailer, a statement from Customs officials said.
"The examination resulted from risk profiling by Customs. The driver was released following questioning," the statement added.
The cigarettes are valued at €152,500, with a potential loss of revenue mounting to €121,750
The Superking, Regal and Sovereign brands are believed to have been destined for the Northern Ireland market.
In November 2002 officers found 702,640 cigarettes concealed in the floor and ceiling of a refrigerated trailer were discovered, and in August 2003, 575,900 cigarettes were found in the floor of another refrigerated trailer.