It found that children who are smacked before the age of six perform better at school when they are teenagers.
They are also more likely to do voluntary work and to want to go to university than those who have never been physically disciplined.
But the study also revealed that children who are smacked after the age of six were more likely to exhibit behavioural problems, such as being involved in fights.
Smacking is currently banned in 20 European countries, including Germany, Spain and the Netherlands.
In Britain 'reasonable chastisement' in the home is allowed unless it leaves a mark.
But the study, by Marjorie Gunnoe, professor of Psychology at Calvin College in the U.S. state of Michigan, found there was not enough evidence to prove that smacking harmed most children.
She said: 'The claims that are made for not spanking children fail to hold up.
'I think of spanking as a dangerous-tool, but then there are times when there is a job big enough for a dangerous tool. You don't use it for all your jobs.'
Professor Gunnoe questioned 2,600 people about being smacked, of whom a quarter had never been physically chastised.
The participants' answers then were compared with their behaviour, such as academic success, optimism about the future, antisocial behaviour, violence and bouts of depression.
Teenagers in the survey who had been smacked only between the ages of two and six performed best on all the positive measures.
Those who had been smacked between seven and 11 fared worse on negative behaviour but were more likely to be academically successful. Teenagers who were still smacked fared worst on all counts.
Parenting guru Penelope Leach disagreed with the findings.
'No good can come from hitting a child,' she said. 'I do not buy this idea that children will learn positive behaviour from being smacked.
'The law says adults hitting adults is wrong and children should be protected in the same way. Children are people too.'
But psychologist Aric Sigman said: 'The idea smacking and violence are on a continuum is a bizarre and fetished view of what punishment is for most parents.
'If it's done judiciously by a parent who is normally affectionate and sensitive to their child, our society should not be up in arms about that. Parents should be taught to distinguish this from a punch in the face.'
Two years ago, Britain was criticised by the UN for failing to ban smacking in the home, after experts said it was a form of abuse.
And growing numbers of the public seem to agree: A recent poll found 71 per cent of parents would support a ban on smacking.
Via the Daily