Doctors and lawyers are calling for people who use drugs to be given healthcare appointments instead of court dates.

A mayor with a front-row seat to the most liberal drug decriminalisation policy in the US will join experts and decision-makers at a landmark Australian forum aiming to build consensus on how drug use and its associated harms will be managed in the coming years and decades.

They will join representatives from almost 300 organisations and dozens of politicians on Wednesday for the Sydney leg of the NSW Drug Summit.

Approaches to treatment and rehabilitation will be discussed at the NSW Drug Summit. (Dean Lewins/AAP PHOTOS)

Royal Australasian College of Physicians president Jennifer Martin said addressing drug use would require funding for treatment services, including for the trauma that could prompt people to start using drugs.

Reducing stigma around use would make it easier for those in need of treatment to seek help and decriminalisation would prevent long-lasting adverse impacts associated with the justice system, she added.

"There is no one silver bullet that will fix the issue ... a health-focused approach requires a comprehensive understanding of interconnecting issues," Professor Martin said.

While Australia addresses drug use through the lens of harm minimisation, reform advocates have urged NSW to go further with wider decriminalisation for personal use and improved support for rehabilitation services.

Ted Wheeler is expected to outline the risk of doing one without the other.

The mayor of Oregon's largest city has said addiction rates and overdose rates skyrocketed in Portland after possession for personal use was decriminalised in 2020.

Rather than being sent to court or jail, people caught with a small amount of illicit drugs were fined up to $US100 ($A155).

The state backtracked in April.

"To decriminalise the use of drugs before you actually had the treatment services in place was obviously a huge mistake," Mr Wheeler told the New York Times at the time.

Large numbers of children in NSW are impacted by parental drug use, welfare agencies say. (AAP PHOTOS)

The summit is also expected to hear about holistic approaches to rehabilitation, including catering for families.

"There are clearly large numbers of children in NSW who are impacted by parental drug use," the Association of Children's Welfare Agencies said in a submission to the summit.

"However, there are very few services that can provide whole-of-family support and even fewer residential rehabilitation and withdrawal management services that can allow parents to bring their children."

Input is also expected from the National Drug and Alcohol Research Centre, law and order bodies, people with lived experience of drug use and those involved in the 1999 drug summit.

Data published by the summit suggested the number of people going through the justice system for drug use and drug possession incidents in NSW was declining - to about 22,800 in 2023.

About half were for cannabis, although one in three of those users were sent down diversionary pathways.

Law Society of NSW president Brett McGrath said cannabis cautions and diversions were a positive step towards a health-based approach to drug reform, and backed further investment in rehabilitation services.

"Investment in rehabilitation services, particularly in regional, rural and remote areas of NSW, coupled with criminal law reform, will contribute to improved community safety and relieve strain on the police and courts," he said.

The society also supports reinstating a youth drug and alcohol court and expanding to the existing children's court the Magistrates Early Referral Into Treatment program, both products of the previous drug summit.

By Jack Gramenz and Luke Costin in Sydney