The opposition has attacked the purchase of the custom-made furniture, saying ACT taxpayer funds could have been better spent on other much-needed resources for the service.

The specially designed tables for the dining room and reception area cost $30,900 each.

Health Minister Katy Gallagher, in response to a question on notice from a Legislative Assembly committee, said the tables were a non-standard design, made from solid, heavy materials "to meet consumer safe and durable design criteria".

Ms Gallagher said the tables featured a very heavy top and solid spotted gum legs "to ensure the robustness and heaviness required".

Opposition health spokesman Jeremy Hanson said $31,000 was a lot to pay for a table.

"Given the recent issues surrounding the adult mental health unit this is an extraordinary amount of money to spend on a piece of furniture," he said.

"The government now needs to reveal the reason behind spending this amount of tax payer's funds on a dining table."

But ACT Health director general Dr Peggy Brown said the seven-by-seven-metre tables had to meet special requirements at the unit.

She added that the price compared quite favourably to other custom-made pieces of furniture.

"It is a very large table and also, quite clearly, in that environment it needs to be made so that it's very solid, very heavy and not able to be turned over and used as a weapon or anything like that," she said.

"For that reason it had to be custom made and it's not a standard design.

"What we were looking for was that it was safe and durable."

Dr Brown said the directorate had also tried to furnish the unit with items that added to the therapeutic environment and did not look institutional.

"I personally think, yes, it's a substantial amount of money but it's a piece of furniture that will be there for a very long time and is built to last," she said.

"I think you would find it would compare quite favourably to a custom piece of furniture of that size."