Officers have said that Theo, 17, was last seen on January 30.
A spokesperson for Sussex Police said: “Have you seen missing Theo from Brighton?
"The 17-year-old was last seen on January 30 at 10.45am.
"Theo is 6’ with dark brown curly hair and brown eyes and was last seen wearing a grey Canada Goose jacket and dark grey trainers.
"He has links to Worthing, Horsham, Southampton and Surrey.
"If you see Theo or have anyone information about his whereabouts, phone 101 quoting of 1475 of 30/01.”

1. Theo, 17
Sussex Police said that Theo, 17, from Brighton, was last seen on January 30. Photo: Sussex Police