Jewellery worth £20,000 was stolen from a house in Broughton - while its elderly occupant was away.
Police have blasted the thief, who they believe purposefully targeted the woman's home in Whittingham Lane, as 'utterly despicable'.
The burglary happened at some point between Wednesday, May 31, and Sunday, June 4.
Among the items taken were gold diamond rings, bracelets, and necklaces, as well as some costume jewellery.
Officers have called on anybody with information, including those who may have been offered it for sale, to report what they know.
PCSO David Reid, from Preston Police, said: “We believe that the house was targeted whilst the woman was away and the offenders have gone in for the jewellery in particular as no other items were taken.
"To think that someone would deliberately do this to an elderly woman is utterly despicable.
“These pieces of jewellery are highly sentimental to the owner and so we would love to be able to reunite her with her things which she has collected over many years."
Information can be reported to police by calling 01772 863390, quoting reference number 1438 of June 4.