A groundbreaking study will investigate community use of cannabis-based extracts to treat children with severe epilepsy.

Australian researchers are reaching out to parents who have been willing to break the law for the sake of their very sick children, to investigate the use of medicinal cannabis in epileptic kids.

A substantial number of Australian families have found dramatic benefits in treating their children with small doses of oils and liquid extracts that are derived from the cannabis plant.

These illegal substances are often taken in addition to conventional antiepileptic drugs.

Now researchers from the University of Sydney, in partnership with Epilepsy Action Australia, are launching the PELICAN study (Paediatric Epilepsy Lambert Initiative Cannabinoid Analysis), which will take an in-depth look into the use of cannabis-based extracts in treating childhood epilepsy.

It will involve interviews with parents who are already using illegal cannabis-based extracts to treat their children.

The study will also involve chemical analysis of oils and extracts already being used in the community.

Professor of Psychopharmacology Iain McGregor from the university's Lambert Initiative says they have great sympathy for these parents who "often inhabit a twilight world of incredible stress and uncertainty" to do the best by their sick child.

Trial co-ordinator Anastasia Suraev says all parents want for their child is to live a normal, happy life and most of them have tried conventional treatment options before trying cannabis-based extracts.

"This has the potential to help uncover new and more effective medications for treatment of childhood epilepsy," Miss Suraev said.

Thanks to scientific advances, researchers now know a lot more about the medicinal benefits of cannabis, which has increased the legitimacy of its use in the medical field.

Cannabis-based oils and liquid extracts contain more than 100 different cannabinoid compounds but different strains of cannabis can have vastly different cannabinoid profiles.

Prof McGregor says only one cannabinoid, known as THC, gets people stoned but there are many others that potentially have therapeutic benefits, which makes this new study crucial.

He say the PELICAN study has potential ramifications regarding legislative change and medicine development.

"Cannabinoids appear to be providing extraordinary therapeutic effects in some children with paediatric epilepsy, but we lack a clear understanding of how they are achieving this," he said.

"Through the PELICAN study, we will gain a better understanding of the cannabinoid components that provide these therapeutic effects, potentially leading to new medicines that could prove extremely effective."