ranchellie Margaret Cadwell, one of the first women to own a national advertising agency and a strong advocate of change in the image of women in advertisements, died on Sunday at her home in Manhattan. She was 70.

Michael Raab, 1998 Franchellie M. Cadwell

The cause was brain cancer, said her friend and financial adviser Richard L. Koenigsberg.

Known in the advertising world as Frankie, Ms. Cadwell used her prominent position to press for changes in how women and older people appeared in advertising.

"Advertising makes women look as if they have the mentality of a 6-year-old, or else they're suffering from brain damage," Ms. Cadwell said at a luncheon in 1970.

That year Ms. Cadwell polled more than 600 women visiting Disneyland on their most-hated commercials, producing a list of spots for products like Scope mouthwash and Bold detergent that the women found insulting. She argued that women could better be persuaded to buy products by presenting interesting facts about the products, and she urged women to avoid buying products with poor or degrading advertising.

She also represented clients in the fashion and cosmetics businesses, saying that women liked to feel beautiful. One of the most familiar lines from campaigns for her clients defended the synthetic nature of Dynel, an imitation fur, by saying: "It's not fake anything, it's real Dynel."

Ms. Cadwell also helped develop advertising for the introduction of the Reach toothbrush from Johnson & Johnson , a forerunner of today's heavily advertised toothbrush brands. The Reach campaigns for many years included a character with a comically oversized mouth.

Franchellie Margaret Cadwell was born on April 23, 1933, in Hamilton, Bermuda. She earned a bachelor's degree at Cornell University, where she later helped found the President's Council of Cornell Women, and an M.B.A. in marketing at the New York University Graduate School of Business.

She left her first advertising agency, Trahey/Cadwell, in the early 1960's to form Cadwell Davis, a boutique subsidiary of Compton Advertising, with Ms. Cadwell as president and Hal Davis as creative director.

For more than 20 years, the agency worked on various accounts for Johnson & Johnson, including O.B. Tampons and Act mouth rinse.

Saatchi & Saatchi acquired Compton in 1982; Ms. Cadwell and a later partner, Herman Davis, bought back the agency, by then known as Cadwell Davis Partners, in 1994. It closed last fall after Ms. Cadwell had been sick for more than a year.

No immediate family members survive.