Some Welsh kids tell us what they think about the advice
Kids in Wales are being advised to text rather than make calls on their mobiles, because no-one knows whether they can damage your health.
There is no evidence at the moment that mobiles cause harm, but the country's leading doctor says it's "better to be safe than sorry".
Leaflets are being sent into all schools in Wales with advice for young people - including keeping conversations short and using hands free.
So what do YOU think? Do you ever worry about mobile phones making people ill?
Which do you do more - text or chat? Do you think the campaign is a waste of time or sensible advice?
This page is now closed. Here are some of the comments you sent in.
"I am not worried because I do not have a phone."
Jack, 7, Middlesex, England
"I am really worried because calling people is my life!"
Charles, 13, London, England
"I have a phone but I don't call because it costs too much. I am worried about it though."
Tara, 10, Ireland
"I am not worried. What are the dangers!"
Megan, 10, Belfast, N. Ireland
"Noooooo!! I don't believe that a tiny little phone can harm peoples health!"
Hiroaki, 8, Tokyo, Japan
"Noooo. Everyone uses mobile phones and has done for ages. What on earth are the dangers?"
Rhiannon, 14, Wolverhampton, England
"I am worried about my friend because she always calls. I always text, so hopefully I will be OK!"
Elizabeth, 11, Manchester, England
"I am not worried because I do not have a phone."
George, 8, London, England
"I was going to get my first phone at the weekend, but now I am very reluctant. Hopefully I can fake being ill or something and get out of getting one! Wish me luck, that's how worried I now feel!"
Henrietta, 11, Surrey, England
"I don't have a phone because I am 10 years old for goodness' sake! But my sister does and it worries me how much she calls. All I see her doing is calling one of her mates!"
Mary, 10, Essex, England
"It is a good idea sending out leaflets, but how exactly do mobiles damage your health?"
Anne, 13, London, England
"I think that if you already know how to use mobile phones properly then it will not damage you, and if you don't know how to use mobile phones properly then you should read the leaflets."
Imogen, 14, England
"I call quite a lot, but the calls are not very long. So hopefully I will be OK!"
William, 12, Lancaster, England
"What? Help! I am always calling, about five or six times a day and they're relatively long calls!"
Courtney, 14, Liverpool, England
"I don't get it. How do phones make you ill? It's bonkers!"
Natalie, 12, Lancashire, England
"I think that the theory makes no sense whatsoever. But that's just me. I'm sure the doctors will figure it out."
Laura, 11, Cardiff, Wales
"I have a mobile phone but I only ever text people on it because I'm not allowed to call."
Isabel, 12, Aberdeen, Scotland
"It's good to be on the safe side but you could say, for so many things, that they can damage your health etc, so I don't think there's anything to worry about until they have evidence."
Sophie, 13, London, England
"I think it's a good idea for leaflets to be put on walls. My sister has a phone but she texts all the time!"
Naomi, 8, London, England
"I don't worry because we are older and capable of keeping ourselves safe."
Naimh, 9, Staffordshire, England
"I think that the leaflets are a good idea because it tells kids our health when using mobile phones. But I don't think kids will listen because we can't really be bothered to read leaflets, it needs to be displayed in a different way, so that the people running this scheme can get the information across. Such as, making adverts for TV or making adverts for popular radio channels."
Sophie, 12, London, England
"One person says it's fine to call, then a month later, a new report comes out saying it's unhealthy to call... So, what's the truth?"
Rebecca, 14, Hampshire, England
"I'm not allowed a mobile until I'm 13, so I don't worry much. But I do worry about other people's safety."
Holly, 10, Durham, England
"I always have to have my phone underneath my pillow and have done since I was 10 and it has not done any thing to me!"
Emma, 12, East Sussex, England
"No, I'm not worried but I don't call much at all."
Rory, 11, Newcastle, England
"I think the leaflets are a good idea because they make kids aware of the consequences of using mobile phones a lot. I am lucky though, I always text!"
Stephanie, 14, Leicestershire, England
"I think it is a waste of time telling us because we already know!"
Whitney, 14, Essex, England
"I wasn't worried about mobile safety, but I am now after reading the report, because I call and hardly ever text. I am going to cut down now!"
Tess, 14, London, England
"I think that practically all things may have unknown risks, so why do adults rant on about this?!"
Abi, 12, England
"I don't have a mobile phone. My mummy won't let me have one."
Christa, 7, Norfolk, England
"I have an iPhone and I'm to addicted to it, but now I have stopped."
Darshil, 12, London, England
"I text rather than phone, because it could be unhealthy, and also because it's cheaper to text."
Bethy, 13, Brittany, France
"I have an iPhone and I am addicted to it. I am now slowly starting to get over it and am only using it to text. I don't call anyway since I have a pay-as-you-go mobile."
Lucy, 14, London, England