William A. Leonard has been chosen to succeed Richard Salant as president of CBS News and Salant retires in April 1979.

Leonard has become well-known here as CBS vice president, Washington - the corporation's principal lobbyist on Capitol Hill - since November 1975. But prior to the assignment he worked for CBS for 30 years as a correspondent and a news producer and executive.

Because he is 62 years old, Leonard faces retirement himself two years after he begins the job, and there had been speculation that if he got Salant's job he would be in a caretaker position until someone younger had been groomed for the top.

But CBS/Broadcast Group President Gene Jankowski yesterday denied that Leonard would be simply an "Interim" president. Asked if this meant Leonard would launch new initiatives, Jankowski replied, "absolutely" but declined to comment what they might be. He added that Leonard would also continue "to carry on the legacy" of CBS News.

Prior to next April, Leonard will occupy the new job of executive vice president and chief operations officer of CBS News. As "the No. 2 man," said Jankowski, Leonard will "call a lot of the shots."

Jankowski made the announcement to about 400 CBS News employes in New York yesterday afternoon, and the ceremony was broadcast on closed circuit to CBS News employes here and later to CBS affiliates throughout the country.

Leonard assured his new charges that that the corporate leaders of CBS regard the news operation as "at the very heart and soul of the body that is this corporation" and that CBS News would remain "independent and unafraid."

He paid tribute to Salant's "influence, his courage, his marvelous mind," and Salant responded with a "welcome home to someone I really love." Salant said he is "certain there will be an orderly transition."

Leonard joined WCBS in New York as a reporter after Dartmouth and World War II Navy service. He covered three political conventions. He joined CBS News in 1959 and was in charge of documentaries, special events, political campaigns and elections from 1964 to 1971. As one of his duties, he helped develop "60 Minutes." From 1971 to 1975 he was senior vice president of public affairs broad-casts for CBS News.

Others rumored to have been in the running for Salant's job were CBS Evening News executive producer Burton Benjamin and CBS News senior vice president William Small. No one was "named to replace Leonard here.