Fairfax Media has previously reported that the inner west hospital is in urgent need of an upgrade, with at least one possum having entered the main building through its leaky roof.

A Sydney Local Health District spokeswoman confirmed that two possums were caught in the roof space of the hospital on Friday morning.

"Following recent reports of possible possum activity at Concord Hospital, two traps were set by a licensed pest controller in roof areas where activity was suspected," the spokeswoman said.

"There have been no sightings of possums in patient areas, or any evidence of further possum activity on the campus."

The possums, the spokeswoman said, were returned safely to bushland.

"Concord Hospital is located in a bushland setting and we will continue to conduct routine inspections."

Concord is the only tertiary hospital in the state not to have been upgraded in the past 20 years.

A 2015 Strategic Asset Plan for the hospital found that the facility had not kept pace with demand, with asbestos in the pipes and World War II era wards.

"The majority of CRGH theatres are at least 40 years old," the report said.

"Many are undersized, and critical infrastructure services such as suction and theatre lights are under capacity or unreliable. There is an urgent need to upgrade theatres, theatre and imaging equipment and amalgamate storage areas to provide a more functional layout."

Health Minister Jillian Skinner committed to a $150 million redevelopment of Concord Hospital last March, with work to start this term of government.

The funds are are about half of what is needed to complete the works and the Baird government has also lobbied the federal government to match its contribution to the upgrade.

"Planning is progressing well, with Sydney Local Health District and Concord Hospital continuing to work with its clinicians to ensure the new building meets the needs of the growing population," Ms Skinner said last month.

But Labor MP Jodi Mckay said the capture of possums was a further sign that the facilities were substandard and in need of an urgent upgrade.

"This is yet another possum in Concord Hospital. This possum issue has been going on for a number of years," Ms McKay said

"The hospital is so badly in need of an upgrade – which is what we've been pushing for – that you've got vermin in the roof and that has been the case for a while now."