This is when the figures are compared with the same period last year. The number of trips by people from Great Britain fell by 3.4% to 735,200.
However, there was an overall increase of 0.7% with 1,817,300 visitors coming to the country. Visitors from North America increased by 0.6% to 305,700 and trips made from the rest of Europe went up by 3.8% to 672,400.
From the rest of the world, there was an increase of 11.9% to 104,000 trips made.
During this timeframe, less people from Ireland made overseas trips with a decrease of 1.5% to 1,727,500.
When putting together the total number of trips (Irish residents' trips overseas plus trips to Ireland), there was a decrease by 0.4% to 3,544,700.
This differs from the previous year where there was an increase of 10.7% from the same time in 2010.
Tourism Minister Leo Varadkar said "These latest figures show that everyone's efforts are paying off in the face of continuing economic uncertainty in most of our major overseas markets.
"We are working with Tourism Ireland to sell Ireland overseas as a visitor destination, and with Fáilte Ireland to continually strengthen our product. I remain confident that we will deliver growth during 2012 for this vital industry."
Commenting on the CSO figures Niall Gibbons, chief executive of Tourism Ireland, said:" Global economic conditions, and in particular the ongoing problems within the Eurozone, continue to present a challenging environment for travel to Ireland, as reflected in today's CSO figures which are flat for the first six months of the year.
"However, within today's figures there are a number of encouraging indicators. The second quarter shows an improved performance on the first quarter; and the month of June alone has seen overall growth of several percentage points when compared with June 2011, including from the important GB market.”