In its survey of over 800 detainees across Australia last year, or 23 per cent of people entering the prison system either on remand or in full-time custody, the Australian Institute of Health and Welfare found that 89 per cent of Canberra's prison entrants had been illicit drug users in the previous 12 months.

Tasmania was the second highest with 86 per cent, followed by Victoria with 83 per cent.

New South Wales did not provide data for the health and welfare survey.

Remandees to prison made up three-quarters of the survey's ACT respondents.

Cannabis and methaphetamine were the two most common forms of illicit drugs used by incoming ACT detainees. Cocaine use was also high with 10 of the surveyed detainees admitting to its use.

Multi-substance abuse across a range of illicit drugs was also commonplace.

Just 6 per cent of the ACT respondents were methadone users when they entered prison.

However, a 2018 survey of detaineee opioid use by the same health organisation revealed that methadone use escalated significantly when people entered the ACT prison system, with 114 prisoners or almost a quarter of the entire Canberra prison population, reported to be on the heroin-replacement drug.

The ACT government's justice directorate described the AIHW report as a small sample size, "taken from a group that may not be representative of the population" of the prison.

"It is also a self-identifying survey, and this may alter the results accordingly, especially when compared like-for-like with other related reports."

Tobacco smoking remains a contentious issue across the prison system because of the high smoking rates among prisoners compared with the general population.

Of those surveyed, 74 per cent of people entering the ACT prison system admitted to being daily smokers, which is among the highest in the country. But smoking rates increased to 93 per cent among those leaving Canberra's jail, even though most reported they had sought counselling, nicotine replacement or other quitting support services while inside.

ACT Corrective Services said it continued "to support the objective of a smoke-free correctional centre in line with other Australian jurisdictions".

It said that it allowed prisoners to smoke "in designated areas, and at designated times".

Of the 492 prisoners in the ACT last year, 110 visited the prison clinic during 2018.

Anti-depressant drugs were the most commonly prescribed, followed by drugs used in opioid dependence.

Dental treatment, pathology, and alcohol and other drug-related issues dominated the health problems managed inside the jail. Most of those leaving prison rated the standard of health care they received as being either "excellent" or "good".

The survey also highlighted the ongoing issue of recidivism in the ACT; how it began with juvenile detention and increased into adulthood.

Of the 35 adults who took the survey as they entered Canberra's prison, 29 per cent - higher than other states and territories which supplied data - reported they had been in juvenile detention, significantly higher than the national average.