Kian was last seen in Worthing on Thursday afternoon, October 7.
A Sussex Police spokesperson said: "He is described as white, 5'11", of medium build, with brown hair, was wearing a white t-shirt, black tracksuit pants, and was carrying an orange Sainsburys bag.
"If you have seen Kian or know where he is, please contact the police on 101 quoting serial 622 of 07/10."
