NEW YORK — CBS Radio is gaining L.A. radio stations KLSX-FM and KRLA-AM in a swap for stations in Boston and Philadelphia.

The radio giant will gain the two stations in a swap with Greater Media, which in return gets WBOS-FM and WOAZ-FM in Boston and WMMR-FM Philadelphia.

With the deal, structured as a tax-free exchange, CBS will own eight stations in L.A., the country’s biggest radio market, and 78 in total.

KLSX, a younger-skewing talk station acquired by Greater Media in 1979, and KRLA, an oldies station last sold in 1985 and licensed to Pasadena, will provide CBS’s radio advertisers with added alternatives to its existing station lineup: KCBS, KNX, KFWB, KROQ, KTWV and KRTH.

“This combination will offer advertisers a strong alternative to advertising in the Los Angeles Times,” said CBS Radio’s chairman-CEO, Mel Karmazin, in a statement.

Jim Duncan, publisher of Duncan’s Radio Market Report, said the L.A. consolidation bumps CBS’s share of the market’s radio revenues from 29% to 32%, with a total of $168 million in 1996, but reduces its share in Boston from 41% to 35%.

Although KLSX carries Howard Stern’s morning show, already syndicated by CBS, both stations “could use some work,” Duncan said. But given the L.A. market’s top position in radio, “any station is decent that has a strong signal” there.

CBS parent Westinghouse had earlier agreed to divest WBOS and WMMR under terms of a deal with the FCC that granted it approval to buy Infinity Broadcasting, since the combined companies’ holdings exceeded current ownership limits in those markets.