IF YOU’RE WORRIED that American cinema has been corrupted by Madison Avenue hucksterism, last week’s announcement that the Tribeca Film Festival is aligning itself with Advertising Week — an annual ad-industry schmoozathon modeled on Fashion Week — may come as bad news. 

But the partnership is just the latest sign that advertising and entertainment are seeping together to a degree nobody thought possible even a decade ago. And despite their obvious disparities — Advertising Week is about salesmanship, the Tribeca fest about movies — these two events have plenty in common.

Each is a sprawling, hard-to-navigate circuit of screenings, keynotes, parties and gaudy traffic-stopping spectacles.

Last year’s Ad Week began with a parade through Times Square of life-size advertising icons — Tony the Tiger, Mr. Peanut and the Geico gecko — and ended with a Lincoln Center gala in which Jon Stewart traded barbs with magazine editors (“Why is your magazine so gay?” he asked Men’s Health editor Dave Zinczenko).

This year’s Tribeca fest is casting a wide net across lower Manhattan with 764 screenings, more big-time studio premieres (“Poseidon,” “M:I3,” “United 93”) than any film festival this side of Cannes and an array of new-media experiments designed to showcase the event’s corporate sponsors. American Express will stage a “15-second clip” competition; Nokia is sponsoring a series of interviews with artists shot on its N series “smart phone,” a multimedia device that looks like a video iPod on steroids.

ONE OF THE ARCHITECTS of the Tribeca-Ad Week partnership is Joe Perello, a former New York Yankees marketing executive who now serves as chief marketing officer for the city of New York.

Perello has a tough job. He was appointed by Mayor Michael Bloomberg to generate hundreds of millions of dollars from corporate sponsors. That’s harder than it sounds. It’s not like he can just rename Central Park Nike Field or the Brooklyn Bridge the Pepsi Skyway. He engineered a deal to make Snapple New York’s official iced tea, but even that arrangement has come under fire.

But Perello’s involvement highlights the overlapping cultural agenda of the two events. The Tribeca fest and Ad Week were both developed in the wake of 9/11 under the nurturing wing of the Bloomberg administration at least in part to boost the international profile of one of New York’s signature industries.

AS TO THE BENEFITS of the alliance, the upside for Ad Week is obvious. Ad Week, which runs Sept. 25-29, will use the Tribeca Film Center as a downtown anchor, staging a series of events that showcase the connection between brand-builders and Hollywood filmmakers.

The partnership also lends some legitimacy to a dubious idea that’s lately been making the rounds of Madison Avenue: that ad agencies can serve much the same function as movie studios and broadcast networks.

As 30-second TV spots fall out of favor, agencies are desperate to redefine themselves as media-agnostic content creators. The partnership with Tribeca, Ad Week CEO Ron Berger told me, “is a great way to demonstrate the synergies between two industries that tell stories.”

The benefits for the Tribeca Film Festival aren’t so clear.

The partnership came together too late to have much of an impact on this year’s festival. Tribeca probably doesn’t need any more publicity. And though corporate sponsorship is the lifeblood of any film fest, Tribeca is already bankrolled by as many blue-chip companies as the Super Bowl, among them Budweiser, General Motors, Delta, Apple Computers and Aquafina Water, a division of Pepsi.

There’s no question, however, that cash from Madison Avenue is flowing like groundwater into every crevice of the film industry — offsetting the rising cost of studio marketing campaigns and providing a viable income source for emerging filmmakers experimenting with new technologies.

And for the directors of the Tribeca fest, the alliance has one additional fringe benefit: It gives them a promotional platform in the last week of September — smack dab in the middle of the New York Film Festival, the only local industry confab prestigious enough to give the Tribeca marketing juggernaut a run for its money.