New figures show the number of new private cars licensed for the first time last year fell by 10.5%.
In 2017, 127,045 new private cars were licensed.
The number of used cars licensed rose by 31.9% to 92,508 in 2017 compared with 70,138 in 2016.
The Central Statistics Office (CSO) says this is the highest annual number of used cars licensed on record.
Overall, 219,533 new and used cars were licensed in 2017, and this is the highest figure since 2007.
All but three counties - Cavan, Roscommon and Waterford - showed a decrease in the number of new cars licensed last year compared with the previous year.
Almost half (48.3%) of all new cars licensed in the country were licensed in Dublin (36.4%) and Cork (12.0%) combined.
In December 2017, 601 new cars were licensed for the first time - a decrease of 11.5% compared with December 2016.
The number of used cars licensed in December was virtually unchanged from the same month in the previous year.
The licensing figures also show that Volkswagen was the most popular make of new cars licensed in 2017, at 13,609.
This was followed by Toyota (12,207), Ford (11,660), Hyundai (11,127) and Nissan (9,954).
Together these five makes represent 46.1% of all new private cars licensed.
The most popular new private car model licensed in 2017 was the Hyundai Tucson.
In 2017, 64.9% of new private cars licensed were diesel compared with 70.0% in 2016.
While 4.1% of new private cars licensed were electric/electric hybrid (5,162) - an increase of 63.7% compared with 2016.
There was also a 14.1% decrease in the number of new goods vehicles licensed in 2017, bringing the total to 24,101.