Thi Trang Nguyen and Thi Linh Hoang, both aged 17, went missing from their social care home in Newquay on Saturday 27 April.
A police spokesperson said: “We are appealing to the public to help us locate these two vulnerable teenagers. Both were reported missing from their social care home, and have subsequently caught a train to London.
“Thanks to our colleagues at the British Transport Police, we have managed to secure images of both teenagers at Paddington Rail station at around 7.20pm on the day they were reported missing.
“Both girls are Vietnamese and we are also appeal directly to the Vietnamese community in London to help us with locating these two teenagers.
“If anyone knows of the current whereabouts of either Thi Trang Nguyen or Thi Linh Hoang, or has seen them since Saturday 27 April, please contact Devon and Cornwall Police on 101 or firstname.lastname@example.org quoting log number 1003 27 April”.