Health Minister Mary Harney has confirmed an immediate criminal ban on a list of products sold by head shops.
It follows approval for the move by the EU yesterday.
Minister Harney said the so-called legal highs, which now come under the Misuse of Drugs Act, are dangerous and their sale and promotion has caused huge anxiety to families and communities throughout the country.
On the list are so called "spice" products, BZP and mephedrone.
Anyone found in possession of the substances faces up to seven years imprisonment and/or a fine, while unlawful supply carries a maximum term of life imprisonment.
The Minister for Community, Equality and Gaeltacht Affairs with responsibility for Drugs Pat Carey is denying the move will push people back to drug dealers.
He said the Government had to act in the interests of public safety.
"There are health and safety issues involved in the products here, not just in Ireland but elsewhere," Minister Carey said.
"Young people who have been using these substances have died as a result."