The New Zealand Police and Facebook have launched a new tool to help find missing children.

The AMBER alerts system will allow police to put out information about children believed to be in danger, to Facebook users in the search area.

Two point nine million New Zealander's are active on Facebook, and it's hoped their eyes and ears will now be used if a missing child is believed to be in serious danger.

The alert will go out to every Facebook user in a 160km radius of where the child was last seen., and includes key information such as a photo and anything known about the circumstances in which the child went missing.

A mother whose 14-year-old daughter went missing 34 years ago was at the launch in Wellington.

Kirsa Jensen rode her horse to the beach at Awatoto in Napier in 1983, and has not been seen since.

Her mother Robyn wishes AMBER Alerts had been around back then.

"This is so good.

"I just beamed when I read about it."

New Zealand Police Commissioner Mike Bush said even if it only helps to save one child, it's worth it.