Cardboard boxes fill the shelves lining the walls of the bone room at Glebe morgue. After sometimes decades in cold storage, their contents hold new hope of solving some old and painful mysteries.

In a huge undertaking to reduce the 400 long-term missing persons cases in NSW, skeletal remains held in the mortuary will soon be sent to the United States for DNA testing.

Already police have been gathering DNA samples from relatives of every person reported missing more than one year ago and sending them to a laboratory in New Orleans.

About 120 samples of mitochondrial DNA have been taken from maternal relatives of the missing and 45 sent for analysis. It costs $US1000 ($1300) to analyse a mouth swab and $US1800 to test bone.

Australia's first missing persons DNA database means about 60 of those sets of remains will offer some hope of burying decades of uncertainty.

Janet Draper is someone who won't find answers to her missing son Ian's whereabouts in the collection of almost 200 skeletal remains held by the Department of Forensic Medicine at Glebe. Mrs Draper insisted two years ago police take a sample of her mitochondrial DNA, pre-empting the current project which is expected to take at least another year to complete.

"I did push to have it taken," the 64-year-old says. "I'm a person that's getting a bit older and Ian may not be found for a while yet. I want the police to be sure that he can be identified."

Ian Draper, a barman then 37, was last seen leaving Mt Pritchard & District Community Club at 3am on August 3, 2001. His car was found at Bringelly six weeks later. Mrs Draper believes her son was murdered.

Each year approximately 30,000 people are reported missing in Australia, almost a third of them in NSW. More than 99 per cent of these are found. Last financial year, NSW Police received 9335 reports of missing persons, and 99.4 per cent of them were found, 73 per cent within three days.

All within the 1 per cent or fewer cases which remain unsolved after 12 months are added to the long-term missing. This grows by 40 to 50 a year.

Some will be found alive or their bodies identified, but about 400 people form the core of those missing since record-keeping was standardised in the 1960s.

With genetic profiling being increasingly used to identify human bones, every name on that list represents work sourcing a relative's DNA if a potentially matching body is found.

Gathering that material now will give police a permanent resource that can be used to positively identify or discount any human remains as belonging to one of those 400 names.

Once a broad database is created, police can establish a system triggering requests for DNA from family once any person has been missing for 12 months.

While the database's greatest worth will be in the future when bodies are found, it also provides the potential to identify some old, unidentified remains.

Dr Denise Donlon, from the University of Sydney, told the Herald the unit considers about 60 sets worthy of extracting DNA to check against the database.

The almost 200 sets of remains in the facility range from those of Aborigines who died before European settlement to a foot found on a beach in February this year. Most were found between the 1960s and 1990s.

A capacity to check any fresh remains against the profiles of hundreds of missing persons would help every family on the database, the missing persons unit's Mark Samways said. "The main thing is we can make the process happen quicker for families," he said. It will take about four weeks to compare a DNA profile against the database.