Researchers have found that acts of affection like hugs and kisses were more important to men than women.
And for women, sex tends to get better over time - after a couple has been together about 15 years.
Researchers surveyed over 1,000 couples from five different countries who had been in relationships for between one and 51 years. Men who reported frequent kissing and cuddling were three times as happy, on average, as those who had less snuggling with their wives or girlfriends. Women, meanwhile, said that such shows of affection had very little impact on their happiness.
Both men and women reported their sex lives improving the longer their relationship had lasted. But men were more likely to say they were happy with their relationship while women were more likely to report being satisfied with the sex. The survey of couples from the US, Germany, Spain, Japan and Brazil was carried out by researchers from the Kinsey Institute at America's Indiana University.
Lead author Julia Heiman said that the first 15 years of a relationship may be emotionally draining for women while they are raising children. As they get older, they have fewer pressures.
"It's possible that women became more sexually satisfied over time because their expectations change or life changes when their children grow up," the Telegraph quoted Heiman.
"The period of less satisfaction seems to overlap with the period of raising children, during which other things really take a focus," added Heiman.
The findings about intimacy were the opposite of what researchers had expected, she revealed.
She said: "We became interested in relationships that endure and how might we begin to understand them.
"Cuddles were more important to men in predicting the degree of happiness. The really useful message is we should not make presumptions about the genders."
"Because there''s no way to be sure we're going to be right in any way."
The study has been published in journal Archives of Sexual Behaviour.