The youngsters are leading a crackdown on smoking in the grounds of Yorkhill Hospital For Sick Children.
Shockingly, the smoke from people standing smoking around the main entrance at Yorkhill travels through air vents and can be smelled in the Schiehallion ward, which treats children with cancer.
The children's play area at the hospital is also littered with cigarette butts.
Smoking in hospital grounds across the NHS Greater Glasgow And Clyde health board area – including car parks, at entrances to buildings, and in green spaces – was banned on March 26, 2007, a year after the ban on smoking in public places was brought in by the Scottish Government.
However, many people flout the law – even lighting up right in front of No Smoking signs.
The rules can only be legally enforced inside buildings, but the health board has tried lots of ways to get people to stop smoking outside.
Automatic voice warning systems are in place at most hospitals and staff often ask people to stop smoking outside – but often get abuse.
The latest drive saw children join health board Tobacco Control bosses to make two short animated films shown on TV screens around Yorkhill.
They show scenes of how the youngsters suffer because of the smoke from people lighting up in hospital grounds.
Julie Rodgers, 15, who suffers from cystic fibrosis, a genetic disorder affecting the lungs, got involved when she was a patient at the hospital.
She said: "It's really bad, with the smoke going up to the cancer ward.
"I think the film is really working because when I went past the place where they usually smoke there was no-one there."
Courtney Sloan, has Crohn's disease and made a Stop Smoking poster during her last visit in the hospital, when she was a patient for six months.
The 11-year-old, from Kilmarnock, said: "I have seen other people's posters and I like the film as well. It's a really good idea."
The children's hard- hitting messages line up with the Evening Times' Clear The Air campaign.
This is run in conjunction with NHS Greater Glasgow and Clyde and NHS Lanarkshire and aims to highlight the risks of Scotland's biggest killer and help people quit smoking for good.
Sarah Barr, 37, Young People's Activities Coordinator, was one of the leaders of the Yorkhill project.
She said: "Young people, particularly the 12 to 15-year-olds, feel really strongly about it."
Children at the hospital also took part in a survey, which found a third of the 170 people questioned did not know smoking was not allowed in the grounds.
Irene Stewart, 43, health improvement practitioner with Tobacco Control, who did the research, said: "All the hospital grounds were smoke-free from 2007 but, like most hospitals, there are issues there with people smoking.
"You can smell it in the wards. From the surveys, the main entrance and the play area were identified as the two main areas where people have seen others smoking.
"There are already signs up at the hospital, including a message from a young patient, saying: "I don't want your smoke – do you want a cancer?'
"We asked people about the signage and that was possibly the one that would make them stop and think, but not necessarily enough to go off site.
"One girl said there was a lot of smoking litter around the play area, so she thought, 'Well, others are doing it, so it must be okay."
"Some people said they had never seen the signs."
Ms Stewart is now looking into new measures to drive the message home, and has set up a competition to get children to design new signs, with the plan for the winner's to be displayed outside the main entrance.
A spokeswoman for NHS Greater Glasgow And Clyde, said: "In the case of staff smoking on our grounds, we have a policy that prevents staff from smoking and we can monitor this effectively.
"Unfortunately, it is more difficult to enforce this policy with patients and visitors. Some people have been abusive to our staff when asked to stop smoking at the doorways of hospitals and on hospital grounds.
"We have used posters and gadgets, such as smoke detectors and automated voice warnings systems, to persuade people not to smoke on our grounds. These measures have had some success, but the problem remains and is of concern to us."
SINCE the Evening Times launched its Clear The Air campaign, the issue of people smoking in hospital grounds has been a hot topic.
Alexander Sim, 64, from Scotstounhill, Glasgow, said he complained after visiting Gartnavel Hospital with a chest infection – and found he had to pass through a crowd of smokers at the door to get outside.
He said: "I had to run a gauntlet of people smoking at the door. I complained about it at the desk and then to the NHS.
"They said people have been complaining so I asked what they were doing, but they did not reply.
"Even people with oxygen masks were smoking."
A father from Baillieston wrote a letter of complaint to the Princess Royal Maternity Hospital about smokers, including staff, around the entrance.
His letter said: "Our new baby's first intake of 'fresh air' in the world outside hospital will be filled with cigarette smoke."
The hospital replied, saying it was an "extremely difficult and sensitive situation to manage".
A patient at the Beatson West Of Scotland Cancer Centre contacted the Evening Times to complain about the number of smokers who light upside that hospital.
He said: "What I find hard to comprehend is why do they allow so much smoking in the grounds? This is a centre of excellence for treating cancer.
"When I go out to the entrance to get some fresh air, inevitably someone will light up next to me.
"It's impossible to avoid it. Patents and staff are doing it. I have phoned to complain and left messages but they never ring me back.
"If people need to smoke there should be somewhere for them to go."
THE Evening Times' Clear The Air campaign, run in conjunction with NHS Greater Glasgow And Clyde and NHS Lanarkshire aims to highlight the risks of Scotland's biggest killer and help you quit smoking for good.
Every day in Scotland 36 smokers die from horrific illnesses such as lung cancer, mouth cancer, strokes and heart disease. Then there is the harm caused to others by secondhand smoke, not to mention the spiralling cost.
For help to stop smoking see our website at www.eveningtimes.co.uk/cleartheair or call Smokeline on 0800 848484. Find us on Facebook by searching for Clear The Air and on Twitter at: bit.ly/etclearair
We are also looking for your stories. Get in touch with reporter Sarah Swain on 0141 302 6532 or send an e-mail to: email@example.com