New car registrations were down by 6% last month, when compared with May 2015.
However, new car sales in the first five months of last year are up 23% when compared to the same period last year.
A total of 99,740 new cars have been sold to date in 2016, according to figures from the Society of the Irish Motor Industry (SIMI).
Commenting on the figurers, SIMI director general Alan Nolan said: "After three years of sustained growth year on year the Industry took a pause for breath in May this year.
"The new shape of seasonality in the Industry is settling-in with the sector now beginning to turn its focus on the 162 period for new car sales.
"Since the introduction of the dual registration plate system, the percentage of new car registrations occurring in the second half of the year has been increasing year on year from 14% in 2011 to 34% last year.
"This new shape to the year does give dealers a better opportunity to focus on used car sales at this stage in the year to help clear the decks in anticipation of the next key sales period for new cars.
"The overall registration numbers are very strong and set the Industry on course for the best registration numbers in over seven years.
"While many manufacturers have started their 162 campaign offerings early, the Industry is still open for business on new as well as used cars in the remaining weeks of the 161 period so consumers can take advantage of attractive deals still to be had in June, so as always our advice is to get out there and shop around!, particularly with the Drogheda and Wexford Motor Shows taking place next weekend."