Fears that the smoking ban could lead to an increase in secondhand smoke in homes have been disproved by a new study in the journal BMC Public Health.
Experts were concerned that smoking parents would be forced out of pubs and bars and would smoke more at home as a result, increasing their children's exposure to secondhand smoke.
But a study by researchers at Cardiff University's School of Social Sciences found that the level of exposure has changed little since before the ban.
The team studied 1,750 children from 75 Welsh primary schools, measuring the levels of cotinine - a marker of cigarette smoke exposure - in their saliva.
Dr Jo Holliday, who carried out the Welsh Assembly Government-funded study, revealed: 'We found that the smoke-free legislation in Wales did not increase secondhand smoke exposure in homes of children aged ten to 11.
'Nevertheless,' she added, 'the home did remain the main source of children's exposure.'
According to the most recent figures from the NHS Information Centre, 21 per cent of over-16s in England were smokers in 2007, down from 39 per cent in 1980.