Today's kids text friends during advertising breaks, use MSN or Facebook when their parents are watching an adult program, or play an electronic game while waiting for their laptop to load up.
Health and exercise researchers at Bristol and Loughborough universities, who carried out the research, say campaigns to reduce "screen time" will only ever work if people understand how chlidren now use technology, and why.
Russell Jago, from Bristol University's Centre for Exercise, Nutrition and Health, said: "The children in this study often had access to at least five different devices at any one time, and many of these devices were portable. This meant that children were able to move the equipment between their bedrooms and family rooms, depending on whether they wanted privacy or company. So simply removing the television from a child's room may not be enough to address the health concerns and we need to work with families to develop strategies to limit the overall time spent multi-screen viewing wherever it occurs within the home."
Of the children studied, three-quarters had access to a handheld games console like a Nintendo DS, DSi or a Sony PSP, seven in 10 to a laptop and half to a smartphone.
Asked how they used them, one typical response was: "On my DSi I'm on MSN and on my laptop I'm on Facebook and then the TV is on."
Television has now become largely a background activity, except when there is something specific on they want to watch.
The study was published in the International Journal of Behavioral Nutrition and Physical Activity.