There are nine sex predators missing from the county but police think they are probably living abroad.
Figures released by 39 forces under the Freedom of Information Act show 394 sex offenders in England and Wales cannot be found. Nine of those are missing from Northants.
Registered sex offenders must keep in touch with their local force and inform them of any change of address but a spokesman for Northants Police said a law change from this week should make them easier to track.
He said: “Of the nine sex offenders whose whereabouts are currently unknown, the vast majority are either believed, or known, to be living abroad - with a number having left the UK to return to their home countries.
“Changes in national legislation which came into force on Sunday, March 8, will make it possible for police forces to apply for orders to ban sex offenders from travelling abroad. It is hoped this change in the law will make the system even more robust.”