However, the group warned that full-year profits could be down 25% on last year's figure of £41.3m, as the broadcaster felt the pinch of the deteriorating advertising market.
For the six-month period to March 31, pre-tax profits fell 18% to £18.3m following a period of investment which strengthened audience share by 8m listeners a week.
The group said its share of commercial hours has grown to 17% from 14% 12 months ago.
CEO David Mansfield remained sanguine about the results. He said, "We believe that national advertisers will increasingly turn to radio to reach their target audiences cost effectively."
The group controls a 29% share of UK radio advertising revenue.