It’s not the kind of cheating most victims had in mind.

As millions of lonely hearts and lusty pants head online to find mates and dates, those who specialize in finding skeletons in the closet are warning online daters to be careful.

This comes a few days after a Toronto human resources firm called for all dating sites to make users supply a criminal background check as part of the registration process.

Ottawa private investigator Robert Gater said that’s “part of a good first step.”

Over the past few years he’s been hired more than a dozen times to find any available dirt on potential boyfriends or girlfriends found online.

A criminal background check will tell someone what their lover has done in the past, but not necessarily what they’re up to now.

That information comes from people like Gater, who do surveillance on top of research.

There are several cases of killers using dating sites to find victims. Investigators in Long Island, N.Y., are currently hunting the so-called Craigslist Ripper, wanted for 10 murders.

The cases in Ottawa appear to be more financially motivated.

“One guy hired me who was in Florida but met a woman online here who said she was in the middle of a divorce, was well-off but her income was in escrow. He lent her money. Sure enough, she’s happily married and was currently doing this to two or three other guys,” he said.

Gater said sometimes he’s asked to get involved before potential victims find out what the motive is — online.

“She sent him back some stunningly attractive photos,” said Gater. “They weren’t of her. She looked nothing like that.”

The woman was also married and was simply taking the photos off a stranger’s public Facebook profile.

“The guy was quite devastated. They had conversations for hours, stringing him along for the better part of the year. He thought she was smokin’ hot.”

Gater figures about 35% of all men on dating sites are married. He said the liars out there are about 50/50 men and women, but they’re after different things.

“Men are looking to cheat or have a criminal record they’re lying about,” said Gater. “Women are doing it for the fantasy or financial fraud.”

Gater said he was hired to check out the “ripped young Greek dude” who turned out to be a short Asian man. When confronted, he claimed he used to be a ripped, young Greek man until he had reconstructive surgery following a motorcycle crash.

“That somehow changed his race and shortened him a good four inches,” said Gater. “Be careful out there.”

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