Many young people believe they could be addicted to using the internet, according to research.
A new study reveals that high numbers of youngsters take gadgets such as laptops, tablets and smartphones, to bed with them, using them to talk to friends, browse websites and play games.
The findings come as a new charter drawn up by the Tablets for Schools charity was published to encourage children to use the internet wisely.
It suggests that young people should resist the temptation to take their device to bed and not use them as alarm clocks, set time limits on how long they use devices and "unplug" themselves at set points in the day or week.
The charity's survey, which questioned more than 2,000 11 to 17-year-olds, found that around two-fifths (39.2%) of those questioned said they "sometimes think they are addicted to the internet".
Older pupils were more likely to say they were sometimes addicted than young pupils.
And nearly two-thirds of pupils (64%) said they took their gadget to bed with them.
Of these, around two-thirds (65.8%) said they used their device at night to talk to friends, with others saying they used it to look at film and picture websites (63.4%), play a game on their own (47.1%), read (32.4%) and do their homework (30.3%).
One 11-year-old girl told researchers: "I can never get off it, and at night I stay up for like two to three hours after I'm meant to be asleep."
Another youngster, a 12-year-old girl, said: "The internet nearly always controls my actions.
"I have been told that I am addicted to the internet, and prefer its company rather than being with other people.
"I feel lost without the internet."
And a third pupil said: "If I had no wi-fi I would have no life."
The poll found that girls were more likely to say they sometimes felt they were addicted to the internet (46% compared to 36% of boys).
It suggested that girls spent more time on social networks while boys said they spent more time playing games, with each gender finding their activity addictive.
The new charter lists five "tips" for students, including "switch off and sleep" and "set time limits".
"Resist the temptation to take your device to bed," it says. "Don't use your device as a clock, invest in a real alarm clock."
The charter also said that students should protect their study time, find new "boredom busters" - activities they enjoy away from using the internet - and dedicate certain times of the day or week to being "unplugged".
Tablets for Schools chair and chief executive of Carphone Warehouse, Andrew Harrison, said: "Previous Tablets for Schools research shows 81% of teachers said they saw a dramatic and positive change in the pedagogical learning of pupils.
"So we know about the incredible force for good tablets are.
"But this Charter of guidance from pupils themselves is invaluable.
"Boundaries can help maintain a healthy relationship with the internet."
The survey questioned 2,228 pupils aged 11 to 17 between January 13 and 22.