The study was carried out by researchers at the University of Otago in Dunedin, New Zealand, led by Erik Landhuis.
The boffins studied the long-term habits and behaviours of more than 1000 children born in Dunedin, between April 1972 and March 1973.
They noted that on an average, kids aged 5 to 11 watched 2.05 hours of weekday television. From age 13 to 15, this increased to an average of 3.1 hours a day.
The researchers noted that both boys and girls showed a 40 percent increase in attention problems associated with "heavy" TV viewers. This result was independent of whether a diagnosis of attention deficit/hyperactivity disorder was made prior to the child reaching adolescence.
"Those who watched more than two hours, and particularly those who watched more than three hours, of television per day during childhood had above-average symptoms of attention problems in adolescence," the New Scientist quoted Erik Landhuis, as writing in his report, published in Pediatrics.
"This suggests that the effects of childhood viewing on attention may be long lasting," he added.
One reason why kids who watch a lot of TV as kids tend to have attention problems may be because the rapid scene changes common to many TV programs overstimulate their developing brain, thus making reality seem boring by comparison, Landhuis suggests.
"Hence, children who watch a lot of television may become less tolerant of slower-paced and more mundane tasks, such as school work," he writes.
Bob Hancox, one of the researchers, said that the study showed the need for parents to limit their amount of TV their kids watch.
"This latest study adds to the growing body of evidence that suggests parents should take steps to limit the amount of TV their children watch," he said.
Symptoms of attention problems included short attention span, poor concentration, and being easily distracted. The findings could not be explained by early-life attention difficulties, socio-economic factors, or intelligence.