Temple Street has become the first children's hospital in the State to become smoke-free.
From today (February 13), smoking will not be permitted anywhere on the hospital grounds by staff, patients, visitors and contractors.
While it is the first smoke-free children's hospital, it joins 18 adult hospitals who have already introduced this rule.
According to Dr Fiona Healy, a consultant respiratory physician at the hospital, smoking is the leading preventable cause of death in Ireland, mainly from heart disease and cancer.
"It is imperative that hospitals are at the forefront of providing an environment that promotes wellness and disease prevention for all. This initiative at Temple Street will ensure a cleaner, safer and healthier environment," she explained.
She added that it would help protect children, their parents, staff and visitors from the dangerous effects of passive smoking.
In preparation for the introduction of the new rule, information has been included in all patient appointment cards since last October, while information signs have been posted throughout the hospital.
Meanwhile, a blue line will be painted around the hospital grounds marking the boundaries of where people will no longer be permitted to smoke.
Commenting on the initiative, Kevin O'Hagan of the Irish Cancer Society pointed out that one in three cancers are caused by smoking and not just lung cancer.
"The other types of cancer linked to smoking are mouth, throat, oesophagus, stomach, pancreatic, kidney, womb, bowel, cervical and bladder cancer," he explained.
He emphasised that smoking not only affects the smoker, but those who breathe in other people's tobacco smoke.
"Children and teenagers exposed to second-hand smoke may be particularly at risk of lung cancer later in life, as well as having an increased risk of asthma and other respiratory problems. So the Irish Cancer Society especially welcomes this progressive initiative in Temple Street," he said.
Today is National No Smoking Day. For advice on quitting, call the National Smokers' Quitline on 1850 201 203.