Commercial's share of listening hours in the January - March 2010 period was 41.3%, down from 42.6% in the fourth quarter of 2009 and from 41.6% in the first quarter of 2009.
The BBC's share conversely increased to 56.5%, up from 55.2% in the fourth quarter of 2009 and from 56.3% in the first quarter of 2009.
Radio achieved a record reach of 46.5 million people, or 90.6% of the UK adult population, listening to a station for at least five minutes during the course of an average week. Commercial radio's reach was 32.2 million people.
Total listening hours did not hit a record, but came in at 1,013,000, up from the previous quarter when they numbered 988,000.
DAB and other digital radio platforms continue to grow in popularity, though not necessarily entirely at the expense of the analogue AM and FM platforms.
DAB listening reached 15.1% during the period while analogue's share of listening was 66.7%, down from 67.5% a year earlier.
Digital's total share (including DAB, DTV and internet) was 24%, compared with 20.1% a year earlier.
Most of its gain came from the unspecified category, which houses listening where the respondent was unsure which platform they were listening to. This category accounted for 9.3% of listening, down from 12.5% a year earlier.
DAB's share came in at a new high of 15.1%, up from 12.7% a year earlier.
Ford Ennals, chief executive of Digital Radio UK, said: "These are extremely encouraging results and represent a real milestone in the UK's transition to digital future for radio."
Andrew Harrison, chief executive of commercial radio body RadioCentre, said: "It is fantastic to see the greatest number of listeners tuning into commercial radio since 2001.
"Commercial radio remains part of the fabric of British daily life, despite the plethora of new devices now competing for listeners' time."