Hospital admissions for childhood asthma fell 18.2 per cent following the ban, which came into force in March 2006.
Researchers studied hospital admission data from January 2000 to October 2009 among children under 15 years of age.
Previous studies had shown respiratory symptoms fell among workers in bars following the smoking ban.
But impact on other groups without occupational exposure to smoke was not known.
Although child asthma attacks were growing by an average of 5.2 per cent per year before the ban, its enactment led to the marked decline in hospitalisation, the researchers found.
The reduction was apparent among both preschool and school-age children.