Ellie Brannen and Reah Hall, both aged 14, were reported missing from home on Tuesday (March 15) and were last seen together in Layton on Wednesday morning (March 16).
But after three days, the pair remain missing and police are growing increasingly concerned for their welfare.
Officers say the girls have links to Preston, but it is believed they might be staying somewhere in the Blackpool area.
CCTV showed the pair together at a local shop in Layton on Wednesday evening (March 16).
Ellie is described as white, of slim build, with long, dark brown hair. She was last seen wearing a black jacket with fur around the hood, a grey tracksuit and Nike shoes.
Reah is described as white, around 4ft 6in tall, of slim build, with blue eyes and shoulder-length light brown hair. She was last seen wearing a red River Island coat with a fur hood, black or grey leggings and black Nike trainers.