Games, chatting and viewing are on screen for young people
Television is now less than half of children's viewing time, in competition with the internet and computer games.
More than one in three children told researchers the possession they could least live without was their computer.
The overall time spent in front of screens by five to 16-year-olds in Britain was nearly six hours a day.
The survey by the Childwise research agency found that YouTube was the most used website, followed by various social networking sites.
The survey of 1,800 children, taken last autumn, found they were spending 2.7 hours per day watching television, 1.5 hours on the internet and 1.3 hours on games consoles.
A casualty of this amount of screen time has been reading, says the annual survey - with 0.6 hours per day on average and with the number of children reading for pleasure in their own time falling from 80% last year to 75%.
In particular, older boys are resistant to reading, with 42% of 11 to 16-year-olds saying they never read books for pleasure.
However playing sport is still a major part of young people's lives - with the survey reporting that it represented 4.8 hours per week.
The survey reveals a picture of children growing up in a youth culture that revolves around screens - used for playing games, watching television and chatting on websites.
Half of these youngsters use the internet at home every day, with a typical session lasting one hour and 45 minutes.
More than a third have internet access in their own bedrooms - and even though parents might have hoped that this would help with their homework, it is much more likely to be used for games, sending messages or watching video clips or television programmes.
Suggesting a shift in priorities, the proportion of children with a television in their bedroom has fallen slightly to 77% - but these are still youngsters who have access to a wide range of channels, with 92% living in multichannel households.
The most watched channels were BBC1 and ITV1, followed by CBBC. Also popular in this age group were Dave, Disney, Nickelodeon and ITV2.