This isn't the Leo you usually read about in the New York Post.

He isn't holding a bottle of Cristal or nursing a wicked hangover from partying past 4 a.m.

He isn't even canoodling with a supermodel -- unless you count giggling in the hallway with Cameron Diaz.

And there's no entourage in sight.

This is a somber, reflective 28-year-old who's anxious to shed his club-hopping, posse-toting, modelizing image.

He's understandably wary about making that case with a reporter from The Post, which has tended to dwell more on his rocky romance with Gisele Bundchen than his Oscar chances.

"I think a lot of people misunderstand me," says the surprisingly real star of Gangs of New York and Catch Me If You Can, whose goatee and greasy hair seem a studied effort to kill the pretty-boy image.

"I don't like to fight every little thing that's said about me because there's no way to control it. It's a losing battle."

What he isn't: "a romantic hero."

What he is: "an environmentalist," he says. "It's the only other thing I've ever really felt passionate about, other than acting."

"Everything you could wish for," says Daniel Day-Lewis, his famously reticent Gangs co-star. "He's a very fine actor."

"A great film actor," says Martin Scorsese, who directed DeCaprio in Gangs. "His eyes say everything."

Scorsese dubs him the next Robert DeNiro, and Catch Me director Steven Spielberg calls him "a very inventive actor" and "his own best critic."

"There were times I'd accept a certain take, and Leo would say, 'No, no, I think there's something I haven't found yet. Let me do it again.' And he would invariably come up with something that was just brilliant," Spielberg says.

Hearing great directors wax eloquent about Leo is all fabulous, of course, but what about the ladies? Where did he and Gisele go wrong?

That's taboo during this interview -- the publicist is lurking nearby.

But let's just say that if the public is as interested in his acting as it is in his love life, he'll pretty much own December.

First up is Gangs -- what Leo calls a "western meets gangster movie" -- in which he plays Amsterdam Vallon, a burly young Irish immigrant in 1860s New York out to avenge his father's murder.

Five days later, Catch Me If You Can will hit screens, offering a svelte and suave Leo as lady-killing teen con artist Frank Abagnale Jr.

"Gangs was definitely the biggest physical transformation I've made for a movie. Ever," says Leo, who worked out for more than a year doing fight training and learning Irish-style boxing.

"The more I did it, the more I became consumed with getting bigger and bigger," he says.

That was nothing compared with the workout DiCaprio got on set in Rome -- clawing at Cameron Diaz during their rage-filled love scenes, keeping his distance from an intense Daniel "Call me Bill the Butcher" Day-Lewis, and watching Scorsese battle daily with Miramax honcho Harvey Weinstein over the ballooning budget and blown deadlines as weeks stretched into months.

"I have to say, even though it wasn't the most 'fun' movie to make, it was truly the most rewarding experience I've ever had," says Leo.

After the epic finally wrapped last March, he had a year to slim down for Catch Me, which "wasn't nearly the kind of physical role Gangs was, in any sense of the word," he says.

"Catch Me was more fun, like a road show," he says. "It felt like an independent movie."

But though Leo says he's anxious to work with the indie film set -- naming Paul Thomas Anderson and Wes Anderson -- these days, if you hear a big director's name, chances are Leo's is attached.

Up next is another date with Scorsese to film The Aviator, based on the life of Howard Hughes, followed by Alexander the Great, with Australian wunderkind Baz (Moulin Rouge) Luhrmann.

Such a résumé undoubtedly will make him the envy of all.

Says Leo, "I can't even comprehend it, honestly. Being able to work with Scorsese two movies in a row is pretty incredible for any actor at any age. I never imagined this would happen."

For more news, entertainment and sports coverage, click here for NYPost.com.