Carwyn Jones, the first minister of Wales, has promised to consider a ban on smoking in cars if levels do not reduce "as a result of the campaign".
The Government cited figures from The Health Behaviour in School Aged Children survey, which claims 20% of 11- to-16-year-old schoolchildren in Wales were exposed to smoke during their most recent car journey.
The campaign focuses on the health risks to children from second-hand smoke and aims to get parents and carers to keep their vehicles smoke-free.
It will span local radio, billboards, bus-backs and bus shelters as well as a dedicated website.
Carwyn Jones, the first minister of Wales, said: "This campaign is clear in its message – smoking in cars poisons your children.
"Wales was the first UK country to vote in favour of a ban on smoking in public places and if necessary we will not shy away from considering legislation to further protect children from second-hand smoke.
"A ban on smoking in cars carrying children will be considered later in this five-year term of Government if smoking levels do not reduce as a result of the campaign.
"We have commissioned research to measure levels of smoking in cars and public attitudes towards it, which will be revisited throughout the campaign to evaluate its success."
The ads were created by artworker Chris Bedford, copywriter Paul Williams, art director Dave Abbott and creative director Martin Bush.