POLICE hold grave fears for the welfare of a Sunshine woman who went missing last week.

Carmen Camilleri was last seen walking alone in Point Nepean National Park around 5pm on Tuesday.

Her green Toyota Corolla was later found in the parking lot of the national park but so far no sign has been found of its driver.

Police are concerned for the welfare of the missing woman, who suffers from a medical condition.

The 42-year-old is described as being 165cm tall, with a solid build. She was wearing a white top, blue jeans and boots and was carrying a plastic bag shortly before her disappearance.

Anyone who may have seen Ms Camilleri or has any information about her whereabouts or disappearance is urged to contact Crime Stoppers on 1800 333 000 or www.crimestoppers.com.au.