Kirsty Holt, 28, from Colne, was last seen in Preston city centre on January 18, say police.
She is usually in regular contact with family members but they have not seen her for some time, they added . She is described by police as white, 5ft 3in tall, slim build with blonde shoulder length hair. She usually wears casual clothing such as a t shirt, jeans and knee length boots. A spokesman for the police said: "We would urge Kirsty to make contact with us or her family so that we can be sure she is safe. Similarly, if anyone has seen Kirsty please get in touch with us." Anyone with information can contact police on 101 quoting log 522 of February 19th.