Ofcom's Children's Digital Day research shows that children aged 11 to 15 are watching one hour and 32 minutes of live TV per day.
Adults watch two hours and 58 minutes per day, the survey revealed.
Older children only consume a fifth of the radio listened to by adults each day - just 15 minutes.
The survey by the media watchdog involved a representative sample of 1,644 UK adults who had to complete seven-day media diaries.
A sample of 186 primary school-aged children (aged six to 11) and 173 secondary school-aged children (aged 11 to 15) completed three-day media diaries.
The study also found that nearly all UK adults reported watching live TV every week over the course of a week (94%).
This compared with just over three-quarters (78%) of children aged 11 to 15 and 90% of six to 11 year olds.
Older children are spending six times longer than adults watching short online video clips on sites such as YouTube and Vimeo (33 minutes versus five minutes).
Children aged between 11 and 16 also spend twice as long communicating via social networking sites than adults each day (52 minutes versus 25 minutes).
Overall, three quarters of children aged six to 15 reported playing games on an electronic device (including games consoles and tablets) during the week. This took up a fifth of children's total time spent on media and communications.
Only 5% of media time was taken up by gaming among the adults surveyed.
Older children watch half the amount of live television per day than adults, preferring to watch content online, new research suggests.