A body has been found in the Blue Mountains during a desperate search for a mother-of-three who was allegedly murdered by her son.

Police launched an investigation into the disappearance of Sandra Popovic, 58, after she failed to return to her home in Sydney's northwest on June 9.

Her son Ante Popovic, 34, has been charged over the alleged kidnapping and murder of his mother.

Family members said they last heard from Ms Popovic at about 4.50pm on June 8, when she told them she was meeting her son in Winston Hills, in Sydney's west.

NSW Police then found a body in bushland near Mt Banks Road, Mt Banks, in the Blue Mountains National Park on June 21 at 2.30pm. 

'The body is yet to be formally identified; however, is believed to be that of the missing woman,' a statement said on Friday.

An extensive search was carried out in the area by police with the help of the rescue and bomb disposal unit, the Rural Fire Service, State Emergency Service and Volunteer Rescue Association.

Ms Popovic's car was found on Dodson Crescent on June 9, when she was reported as missing. 

Two days later, detectives arrested Ante Popovic while he was sitting in a white Toyota Hilux in bushland along Parnell Fire Trail in Tomerong, south of Nowra.

He allegedly had his mother's phone, Superintendent Barry Vincent told reporters at the time.

'It'll be alleged that they were meeting there to talk about perhaps borrowing some money,' he said.

'When the family were informed of the action taken by police... they were obviously shocked.'

He described Ms Popovic as someone who looked after her elderly parents and said she was 'estranged' from her son. 

Ante Popovic did not apply for bail when he appeared in court on June 12. The matter will return to Parramatta Court on August 13.