Donald Marron is so ubiquitous in New York City that it isn’t unreasonable to ask how he does it.

His response is delivered with a smile that comes from his eyes as much as from the rest of his face.

“If you’re enthusiastic about something, you find the time to do it,” Mr. Marron, chairman and CEO of Lightyear Capital, said. “I don’t much think about the energy involved – I just try and do things.”

At 6 feet 6 inches, the health-conscious Mr. Marron probably doesn’t give much thought to where that energy comes from. But then, as far as anyone can remember, he’s always been a creative force – back in his days in the city’s public-school system, back at the City University of New York, back in his Wall Street days when he headed various securities companies, back when he founded Data Resources, a nongovernmental source of economic data.

Yet Mr. Marron possesses the sort of modesty about his accomplishments that doesn’t seem forced.

The latest of those accomplishments is the money he’s raised at Lightyear, a highly successful private equity firm that oversees more than $2 billion. He founded the firm after retiring two years ago as chairman of UBS America, one of the world’s biggest wealth managers. Earlier, he was CEO of PaineWebber for 20 years until its merger with the Swiss-based UBS.

In New York’s world of high finance, Mr. Marron enjoys stellar status. He’s known as much for his business acumen as he is for being one of America’s most prolific private art collectors. He’s also known for creating PaineWebber’s massive art collection – acquisitions so impressive that, like institutions such as the Museum of Modern Art, the collection often went on tour around the country. More than 850 post-1945 works by major American and European artists, including Jasper Johns, Roy Lichtenstein, Willem de Kooning, and Susan Rothenberg, form this collection.

Mr. Marron is known for his long association with MoMA, too, and not only because he arranged for a gift of 44 paintings from the PaineWebber collection to the museum. He’s vice chairman of the board of trustees, and earlier served as president of the 76-year-old institution. Not long ago, he played a significant role in raising nearly $1 billion for its redesign. Some of that money was donated by Mr. Marron himself, along with his wife, Catherine, who is chairman of the New York Public Library. A grateful museum named its stunning atrium – designed by Yoshio Taniguchi – in their honor.

Then there’s his involvement with the Coalition for the Homeless, where he pays special attention to helping the city’s estimated 16,000 children who don’t have adequate shelter.

“It’s very hard for me to accept that in this great modern city of ours, there are children without homes,” Mr. Marron said.

So intensely does he champion their cause that, not long ago, when a group of children he’d helped came to his office in Park Avenue’s Seagram Building and one of them read aloud a poem dedicated to him, Mr. Marron wept.

“You can make an impact on people’s lives in so many different ways,” he said. “America has always been an optimistic country. Americans have always believed in endless possibilities. That’s why there must be more private giving to causes such as the homeless. It’s not acceptable that in American society there should be men, women, and children without the access to health, housing, and education that more fortunate people have.”

This isn’t the kind of talk that one hears from too many titans of business and industry. Mr. Marron leaves the impression that Wall Street’s leaders ought to be doing more to tackle issues such as urban decay.

Such concerns animate Mr. Marron not only because of his belief that the more fortunate have a special obligation toward the dispossessed, but also because an America that’s stronger at home, in his view, can also be a beacon for the rest of the world.

“We really have this world responsibility – we have this obligation,” Mr. Marron said. “We are under a much bigger spotlight, especially those of us in business and finance.”

The reporter asked him what, in light of his reputation, he would say to fellow leaders in finance?

“The vast majority of America’s financial institutions work hard to do the right thing and to do good,” Mr. Marron said. “But that may not be enough. In addition to playing by the rules, we have to take a big hand in making the rules.”