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11 September 2014, 15:00
Smoking in cars where children are present could cost you 50 pounds in the future.
The Welsh Government says on-the-spot fines will come into force next year.
The ban is being brought in to try and protect children from the effects of second hand smoke.
A recent poll from anti smoking group ASH Cymru found 4 in 5 people in Wales are in favour of the move.
Ellen De Lacey is their chief executive. She said: "Babies and young children - they're still developing, they're still growing.
"They breathe much quicker than we do as adults so they're taking in more of that second hand smoke.
"There are key links to things like asthma, respiratory disease, cot deaths. The health harms - from passive smoking, particularly in a car - they're well documented."
A Welsh Government consultation - starting today - is also asking whether a ban on smoking in cars could be extended to e-cigarettes in the future.
Health Minister Mark Drakeford said: "We have real concerns about the ability to enforce a ban on smoking in enclosed places where people then use e-cigarettes. For those who are in charge of enforcing things they're difficulty to distingush and it adds another layer of complexity.