Parents have been warned of the potential dangers of children watching TV while using other interactive devices.
University researchers said children were often "multi-screen viewing" -- watching TV while at the same time using smartphones, laptops or hand-held gaming devices.
A sedentary lifestyle -- linked to spending lots of time watching TV and playing computer games -- is thought to increase the risk of obesity and mental health problems, researchers at Bristol and Loughborough universities said.
It is now possible to watch TV 'on demand' via the internet, play computer games on laptops, hand-held devices or mobile phones, keep in contact with friends using text, Facebook, Skype and MSN, and to do all this concurrently.
Previous studies have not examined if children take part in multi-screen viewing or their reasons for doing so.
The researchers questioned 63 10 to 11-year-olds and found the children enjoyed looking at more than one screen at a time.
They use a second device to fill in breaks during their entertainment, often talking or texting their friends during adverts or while they were waiting for computer games to load.
The television was also used to provide background entertainment while they were doing something else -- especially if the programme chosen by their family was considered 'boring'.
One study respondents said: "I'm on my DSi and my laptop. On my DSi I'm on MSN and on my laptop I'm on Facebook and then the TV is on."
Dr Russ Jago, from Bristol University's Centre for Exercise, Nutrition and Health Sciences, said: "There is a shortage of information about screen viewing among children, especially given the rapid advances technology and their widespread availability.
"For example, TV programmes are watched on computers, games consoles can be used to surf the internet, smartphones, tablet computers and hand-held games play music, video games provide internet access, and laptop computers can do all of the above."
Dr Jago added: "Health campaigns recommend reducing the amount of time children spend watching TV.
"However, 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."
The research paper is published today in the International Journal of Behavioural Nutrition and Physical Activity.