Valentine's Day is approaching, but those looking for truth and romance would be well advised to avoid internet dating sites to meet the man or woman of their dreams, according to a new study.

Researchers at Cornell University found that online daters of both sexes on four popular dating sites often stretch the truth when it comes to disclosing their height, weight and age.

The study, to be published in the April edition of the scientific journal Proceedings of Computer/Human Interaction, found that men regularly overstated their height, while women understated their weight, said Jeffrey Hancock, the lead author of the Ithaca, N.Y., university study.

Using a new research method that measured the difference between information in a profile and verifiable reality, Hancock found that about 52.6 per cent of men lied about their height, as did 39 per cent of women.

When it came to weight, women edged out men for stretching the truth, with 64.1 per cent lying, compared with 60.5 per cent of men.

But men were less honest about their age, with 24.3 per cent lying about it, compared with 13.1 per cent of women.

The 80 study participants — half of them men, half women — were recruited through newspaper and Craigslist ads and selected from Match.com, Yahoo Personals, American Singles and Webdate, where daters make their own profiles and can initiate contact with others.

Their profiles were compared with their actual heights and weights and their ages were determined by looking at their driver's licences.

The researchers decided that categorizing a statement as a lie would require discrepancies in height of about half an inch, of weight by more than five pounds and of age by a year.

The pattern of lying was frequent but subtle, suggesting that lying in online dating profiles is strategic, Hancock said. "Participants balanced the tension between appearing as attractive as possible, while also being perceived as honest."