Hollywood isn’t seeing as much green in 3-D re-releases as it had hoped.

Considered an easy new revenue source after the 3-D re-release of Walt Disney Studios’ “The Lion King” popped out of the screen and grossed nearly $100 million last year, most such follow-ups have landed with a thud in 2012.

Disney’s “Beauty and the Beast” and “Finding Nemo” were both disappointments, grossing $47.6 million and $40.7 million, respectively, in the U.S. and Canada. Twentieth Century Fox and Lucasfilm’s “Star Wars: The Phantom Menace” took in a similarly unimpressive $43.5 million in February. Fox and Paramount Pictures’ “Titanic” grossed a slightly better $57.9 million domestically last spring.

Audiences, it turns out, are very selective about which movies they’ll see again in 3-D. The genre’s few hits were ones that moviegoers, or the children they took with them, hadn’t seen in a long time — or at all. “Titanic,” for instance, grossed almost $150 million in China, where few had seen the original 1997 epic romance.

That makes the stakes high for today’s 3-D re-release of “Monsters, Inc.” Disney executives were particularly disappointed by the weak 3-D box-office take for “Nemo,” one of Pixar Animation Studios’ most beloved and successful pictures. A soft performance by Pixar’s “Monsters” probably would make Disney — and other Hollywood studios — rethink their strategies.

“There’s a certain cultural cachet for parents bringing their kids to movies like ‘The Lion King’ the same way their own parents did for them 20 years ago,” said Vincent Bruzzese, motion picture president at research firm Ipsos MediaCT. “But many of these movies, people have watched it at home with their kids, so 3-D may not be something new or extra enough to pay the exorbitant cost of going to a theater.”

The cost of converting animated movies, particularly those made with 3-D computer technology, is extremely low compared with a new production. Disney spent only about $3 million adding 3-D effects to 2001’s “Monsters, Inc.”

Pixar director of 3-D production Josh Hollander said in a September interview with the website Collider that “Monsters” was “a little easier” to convert than “Nemo” because the movie’s visuals are less complex.

Pre-release surveys show “Monsters, Inc.” is headed for a modest opening, lower than the $16.7-million start for “Finding Nemo.” The best hope for it to perform better than its underwater predecessor is a lack of new releases for families with young children over Christmas.

Still, Disney does not appear optimistic about continuing its recent 3-D re-release spate. It has no more planned after next September’s “The Little Mermaid.”

After the unimpressive showing for “Phantom Menace” in February, Fox and Lucasfilm scheduled the next two “Star Wars” movies just three weeks apart in September and October 2013. That will enable the companies to run one set of commercials to promote both pictures.

“It has everything to do with getting more bang for our marketing buck,” said Fox domestic distribution president Chris Aronson.

Marketing may also be what ends up making the 3-D version of “Monsters, Inc.” a worthwhile release for Disney, even if it barely breaks even at the box office. Right before every showing, audiences will see a trailer for a brand-new Disney animated movie — June’s sequel, “Monsters University.”

And yes, it will be in 3-D.