Bogumila Kovaleski, 84, has Alzheimer's, and was last seen at her home in Watchfield Court in Chiswick at 5.40am on Saturday May 20.
Officers and the family of the pensioner are growing increasingly concerned for her welfare.
She is described as white, of slim build with grey hair and is thought to be wearing a pink long-sleeved night gown and black trousers.
Police believe she may also have a light brown jacket.
Anyone with information relating to the whereabouts of Mrs Kovaleski is asked to contact officers at Hounslow Police, by calling 101.
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