According to a report compiled from more than 206,000 complaints received last year by the US Internet Crime Complaint Center, in 2007 men lost $1.67 ($0.84) to every $1 (£0.50) lost by women in online fraud.
The IC3 is a joint effort run by the FBI and the National White Collar Crime Center.
The IC3 is the clearinghouse for online crime complaints in the US, and its database is used by regulators and law enforcement to get a picture of criminal trends and, in some cases, help hunt down the criminals.
The organisation says that buying patterns and human nature play into the findings.
"Historically men were more apt to purchase large ticket item like electronics... that could explain a lot of it," said John Kane, the IC3 research manager who wrote the report.
But with women now spending more online, the difference is also due to the fact that certain types of schemes seem to suck men in.
"Men tend to fall victim... to business investment schemes and some other schemes that have a higher dollar loss," Kane said.
Investment fraud complaints, where the average loss is more than $3,500, were overwhelmingly submitted by men, Kane said. Compare that to something like auction fraud, where both men and women are frequently victimised. The average loss there is just over $480.
Men also tend to be the victims of cheque fraud (average loss: $3,000) and Nigerian letter fraud scams ($2,000), Kane said.