Foreign nationals now account for 10% of the Irish population, according to the 2006 Census Report published by the Central Statistics Office.
The number of foreign nationals living in Ireland has almost doubled to 420,000 in the past two years.
According to the report, the number of people aged over 65 now stands at 468,000, which represents 11% of the total population.
In every census since 1961 the number of people over 65 in Ireland has grown.
The average age of the State's population now stands at 35.6 years.
Dublin Fingal has the youngest population with an average age of 32.2. Roscommon, with an average age of 38.3 in 2006, has the oldest population in the State.
The Census also shows that divorce is on the increase with almost 60,000 divorced people recorded last year. The lowest divorce rate is in Co Cavan.
The Census also showed that Irish couples are having fewer children.