Passengers under 16 who go through Humberside Airport or Hull's King George Dock will be checked as part of a campaign against child abduction.
Passports will be checked against the missing persons' database
Police will check their passports to make sure the children are not being taken out of the country illegally.
Those not travelling with both parents or legal guardians will need proof of consent so they can leave the country.
Humberside Police said most reported abductions involved children being taken by one parent after a separation.
Humberside Police's Assistant Chief Constable Alan Leaver said most of those children were "unwilling participants" and they were the ones who suffered the greatest from a split.
He said: "Parents from whom the children are abducted are often left unable to locate their children and unable to finance litigation in the child's new country of residence.
"Therefore Humberside Police will do everything possible to keep these children in the UK and in the jurisdiction of the British courts."
Mr Leaver said Humberside could be seen as a convenient and low profile place to travel from, with its ferry links to mainland Europe and air travel to many destinations.
Airport and dock staff will use a passport reader to check outbound passengers while officers will have access to the current child abduction list.
Passports of all travelling children will also be checked against the Police National Computer wanted and missing database.
The month-long operation is being supported by the international child abduction charity Reunite.