Brisbane's CBD office vacancy rate has slumped from a 15 year high of 11.3 per cent in January to 10.9 per cent in July this year, according to the Property Council of Australia's mid-year Office Market Report released today.

This reduction was steered by healthy demand, particularly for A Grade space, said Property Council of Australia Queensland Executive Director Steve Greenwood in a statement.

"Demand over the last six months has probably been above most people's expectations with net absorption almost triple the 20 year average.

According to him, 22,989 square metres of new office space has come online in Brisbane's CBD since January. This was outstripped by net absorption of 27,516 square metres, resulting in the cut in the overall vacancy rate.

"Whilst this is a positive sign that the Brisbane CBD office market may have turned the corner, Brisbane remains well above the national capital city average vacancy rate of 8.9 percent."

At present, Canberra is the only capital experiencing a higher vacancy rate than Brisbane, with both Sydney and Melbourne below the national average, Mr Greenwood said.

"It also appears that the glut of B Grade space in the CBD continues to be an issue. Whilst the B Grade vacancy rate increased only slightly over the period it remains comparatively high at 15.4 percent.

"Interestingly, the performance of Brisbane's CBD office market has varied widely over different grades of space. Vacancy increased for the Premium and D Grade sectors over the six months to July. Over the same period A and C Grade stock experienced positive net absorption, and B and D Grade stock experienced negative net absorption.

"With approximately 38,000 square metres of space due to enter the market in the second half of this year, the big question is whether or not this strong demand will continue and prevent a possible reversing of this recent positive trend," Mr Greenwood said.