Undated (AP) _ The importer of Saab automobiles has picked one of the newer advertising agencies, while The Wall Street Journal picked one of the oldest in a pair of high-profile moves on Madison Avenue.

Saab-Scania of America Inc. said Thursday it had selected Angotti Thomas Hedge Inc. of New York to handle its $25 million advertising account.

The agency was created only five years ago, and the new job boosts its total billings by more than 50 percent from about $45 million.

Its other clients include KLM Royal Dutch Airlines, Wild Turkey bourbon, Kirin beer and Barron's, the weekly business and financial publication that, like the Journal, is published by Dow Jones & Co.

Barrie Hedge, president of the agency, said the agency would get to work immediately on advertising for the model 9000S that Saab plans to introduce in mid-April. The appointment is effective April 2.

Saab-Scania, based in Orange, Conn., said it picked Angotti Thomas over two other New York-based agencies, Kirshenbaum & Bond and Slater-Hanft & Martin.

The account had been handled for the past 2 1/2 years by the agency Lord Einstein O'Neill & Partners, an even younger agency that got the account shortly after it was created.

Lord Einstein is headed by several executives who abruptly quit their old agency, Lord Geller Federico Einstein, in March 1988 after it was acquired by the British advertising conglomerate WPP Group PLC.

''It was time for a change,'' said Roy Steinwolf, ad manager at Saab- Scania, said Thursday in explaining why Saab-Scania launched a search for a new agency in January.

He said Saab sales in the United States have slipped over the past three years, including a 12 percent decline in 1989, after showing steady gains for the previous six years. Sales of European imports generally have been weak.

Saab-Scania has been using the ad slogan, ''The most intelligent cars ever built,'' for several years and Steinwolf said whether to continue that slogan is under discussion.

The Wall Street Journal, meanwhile, said Thursday it had selected an agency that celebrated its 125th birthday last year, J. Walter Thompson, to handle its advertising sales and circulation advertising account.

The daily newspaper declined to disclose how much it planned to spend on advertising this year, although one trade publication estimated it was $7.5 million.

Thompson, also owned by WPP Group, was ranked the eighth-biggest U.S. ad agency in 1988, handling worldwide advertising billings of more than $3.8 billion and creating advertising for products such as Kodak film and Kellogg cereals.

The Journal's former ad agency was GSD&M of Austin, Texas, which had been hired in August 1988. Recent ads from GSD&M described the Journal as ''Faster, Tougher, Smarter.''

GSD&M had been hired to handle advertising during the Journal's centennial celebration in 1989 and to promote and posiution the newspaper's reorganized, three-section format in 1988.

''As business becomes ever more global, we foresee enormous opportunities for the Journal in the '90s and beyond,'' said publisher Peter Kann.

He said Thompson ''has demonstrated that it can help us to capitalize on these opportunities in the years ahead.''

Thompson was believed to have been one of two finalists considered for the job. Insiders who spoke on condition that they not be identified said the other agency was Lord Einstein O'Neill & Partners, the agency that broke away from WPP Group.