Maria Manuela Eanes, 46, of Portugal is the very model of a modern first lady. A former Ministry of Education official and lawyer, she's a veteran of the international conference circuit on social problems, and she's using this trip not only to gather information on drug abuse but also to do some business of her own.

While in the United States, Eanes plans to raise money for the Portuguese Institute for Child Support, a private organization she helped found two years ago that runs programs for sick, abused and poor children..

Eanes' activities in Portugal so far have not specifically involved antidrug programs, but she says, "The problem of drugs in Portugal is as serious as in many other European countries." She believes the growth in drug abuse among the young is a spiritual as well as economic problem.

"With no jobs and no way to occupy their free time and a terrible atmosphere at home, young people feel isolated," she says, speaking through a translator. "There is an inversion of values and young people don't feel useful to the community, so they give up."

Dark-eyed and assured, Eanes says that while she is grateful she is not exposed to the intensity of the spotlight Nancy Reagan is in, she sometimes envies the American first lady's ability to command interest.

"The big difference in the role played by Mrs. Reagan and myself is that the press doesn't pay as much attention as they do here," she says. "I personally prefer to do things with some discretion and not too many people pushing and so on. Then I realize there are some specific activities in the social field where maybe it would be a good thing to have coverage from the media . . .

"For instance, when I go to the poor quarters and we have created a new playground, or if I go to a hospital where it has been remodeled to be more warm for the children, I think it's important for TV to show it. Not for me personally, but it would perhaps inspire people in other parts of the country."

First lady since her husband was elected president in 1976, Eanes, dressed in a hip-wrapped purple silk dress and a string of pearls, says she is the granddaughter of "humble people, peasants who worked in the field." She says she was raised to believe "we only exist when we are useful to our community in a larger sense. The world must be better because each one of us existed."