Cold case probe into WA mum disappearance

It took 16 years for the family of a Perth mother to realise she hadn't simply moved away and now the state's cold case homicide squad believes she may have been "the victim of a serious crime".

Rebecca Anne Delalande, 23, vanished in November 2001 but detectives only learnt about it late last year while investigating an unrelated matter.

Detective Senior Sergeant Craig Stephen says Ms Delalande's family thought she had moved interstate.

"She had infrequent contact with her family and they had formed the belief that she had relocated to the eastern states to establish a new life," he said on Wednesday.

"We believe Rebecca was the victim of a serious crime and we are working hard to establish the circumstances surrounding her disappearance."

Det Sen Sgt Stephen said Ms Delalande faced "challenges" in her life but her disappearance was shocking to her family.

Ms Delalande attended a dental appointment on November 5, 2001 and was last seen at a Seville Grove home a short time later.

She had a six-year-old son at the time, who has since been raised by other family members.