Southern FM has lost 39,000 listeners, despite retaining its position as the most popular Sussex-based radio station.
Latest figures reveal the station had about 333,000 listeners in December last year, compared to 372,000 in December 2001.
The data, compiled by the Radio Joint Audience Research group (RAJAR), reveals 34 per cent of adults listen to the station, compared to 39 per cent last year.
Figures indicate more listeners are tuning in to rivals Juice and BBC Southern Counties Radio than in previous years.
Brighton's Juice saw its listenership jump 3,000 between December 2001 and December last year, from 37,000 to 40,000. However, 3,000 more people moved into its transmitter area in the same period.
Southern Counties Radio has the highest number of listeners, but has a larger transmitter area covering Sussex, Surrey and northeast Hampshire.
In December last year 337,000 people tuned in, compared to 315,000 in 2001.
Southern FM marketing manager Jo Ashton said: "The last few years have been a very competitive time in the radio industry but everyone here is delighted at the way our figures have held up against the competition."
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