TV Guide, the struggling magazine sold last year to private equity firm OpenGate for a $1, has mysteriously dumped the listings for youth-oriented channels the CW and MTV.

For a publication that has heavily covered MTV staples like “The Hills” and CW phenoms like “Gossip Girl,” the move was head-scratching.

TV Guide president/CEO Scott Crystal told the Philadelphia Inquirer that the decision to remove the CW, MTV and a few other channels (such as DIY) were purely based on space.

“There are now hundreds of channels on television and we can only accommodate approximately 70 in our primetime grids,” he told them.

But that explanation doesn’t hold much water: TV Guide still provides listings for tiny broadcaster Ion, as well as cablers Planet Green and QVC. Was Crystal attempting to claim that TV Guide readers were more interested in listings for those than MTV and the CW?

Actually, given the aging demographics of TV Guide’s readers — and the fact that most young TV viewers access listings via their set-top box — the decision to focus on channels that appeal to older demos perhaps is a plausible explanation. (But not a complete one — channels such as teen-oriented the N and kid-friendly Toon Disney are still included).

But if TV Guide is turning its back on younger viewers, that wouldn’t explain why this week’s issue contains a story about the CW’s “Smallville.”

“It’s baffling to us why they want to cover our shows but not tell their readers when we’re on,” a CW source said.

Adding to the mystery: TV Guide is devoting just as much space to listings as it did a month ago, when there was plenty of room for the CW and MTV. The mag even enlarged its listings for MyNet and Ion, which is what squeezed the CW out.

Relationships do appear to be playing a role. The mag dumped its TV Guide Network listings the moment the two companies were separated. And while it may seem strange that there’s room in TV Guide for QVC listings — offering up shows including “Marie Osmond Dolls” and “Limited Quality Linens” — the home shopping channel is a frequent advertiser in the magazine.

TV Guide could not be reached for comment.