A report into Victoria's public hospitals has highlighted many are in a precarious financial position.

Cash levels at 12 Victorian public hospitals were so low last year they only had enough money to last a week.

An Auditor-General's report found 32 hospitals needed letters of financial support from the Department of Health in order to operate as going concerns on June 30 last year.

"The current funding model has resulted in a mismatch between public hospital boards' responsibilities ... and the boards' limited ability to control the funding they receive," the report, released on Wednesday, said.

More than two thirds of public hospitals have a poor capital replacement risk, meaning many hospitals are not replacing assets as they deteriorate.

"This means that services may be at risk in the future due to assets becoming obsolete," the report said.

The Auditor-General was concerned about the 12 hospitals with enough cash to last a week or less on June 30 last year.

"While this is an improvement on the prior year result of 23 public hospitals being in this position, it means that public hospitals are still at significant risk of not being able to fund operating activities," the report said.

Another Auditor-General's report showed public CT and MR scanners were not being managed economically, efficiently or effectively across Victoria.

Patients in Melbourne's north and west waited an average of 60 days for an MR scan, while patients in the city's south waited 27 days.

Those using specialty health services waited just two days on average.

"It is concerning that one hospital can have a wait list of up to 98 days for an MR scan while the waiting time in a hospital less than 10km away is only two days," the report said.

The Auditor-General found most public hospitals were not factoring in future demand when they decided to replace or buy imaging equipment.

Victoria has 87 public hospitals and 23 associated entities.