Consumers from the Republic of Ireland spent €435m shopping in Northern Ireland from the end of June 2008 to the end of June this year.
Most people shopping in Northern Ireland, however, are from the border region.
Of those who made at least one shopping trip to Northern Ireland in the year up to July, 41% live near the border.
Those who live the farthest from the border made the least shopping trips to Northern Ireland (9% from the south-east, mid-west and south-west combined).
Householders said they spent an average of €286 on their most recent trip across the border.
Groceries were the most popular purchase (80% said they bought groceries on their most recent trip), with alcohol next (44%). Clothing and cosmetics were purchased by 42% and and 26% of households respectively.
Less than one in 10 households said they had shopped in Northern Ireland more frequently in the past year than they had in previous years.
This is the first CSO survey on cross-border shopping.
A section on cross-border shopping was included in the Quarterly National Household Survey for the second quarter of 2009.
The total household expenditure of €435m was calculated by combining information on frequency of trips to Northern Ireland and average expenditure on the most recent trip.
No adjustment was made for seasonality.