THREE in four marijuana dealers making more than $1000 on the streets of South Australia are avoiding jail.

Figures compiled for The Advertiser by the Office for Crime Statistics and Research show eight of the 39 people convicted in 2011 of trafficking cannabis served immediate jail terms.

In that time, 29 offenders received suspended sentences.

Yesterday, SA Police Commissioner Gary Burns said sentences must reflect the serious harm posed to the community by drug dealing.

But Acting District Court Chief Judge Geoffrey Muecke said there were benefits to suspension - including preventing young sellers becoming hardened criminals.

The Office for Crime Statistics and Research data encompasses all cannabis-selling offences heard in the Supreme and District Courts between 2007 and 2011.

Those offences are for selling more than 250g of cannabis plant. The Advertiser understands 1kg of cannabis has a street value of about $4000.

In 2011, eight convicted sellers served immediate jail terms with an average sentence of about 63 months.

Two other sellers were dealt with by bonds or fines, while 29 more - or 74 per cent of all sellers - received suspended sentences of an average of 19 months.

In a statement, Commissioner Burns said police took "every opportunity" to put cannabis sellers before the courts.

"It is important that the penalties for dealing in commercial quantities of illicit drugs adequately reflect the seriousness of the offending and the harms done to South Australians," he said.

"Illicit drug use causes harm to individuals, families and communities right across SA. There is a strong association between illicit drug use and crime ... this is of major concern to police."

In an emailed statement, Judge Muecke said there were benefits to allowing sellers to rehabilitate in the community.

"They may include preventing a first-time `low end' offender from hardening in prison and therefore reoffending," he said.

"There may be a benefit to the community by suspending a sentence where the offender is otherwise of good character, in employment and supporting a family.

"Placing that person in prison ... also has consequences on the offender's family, and to the wider community."

Originally published as Cannabis dealers stay on the streets