Graffiti affects almost 40% of streets in Newport but only 2% of Pembrokeshire streets, according to a campaign group.
Keep Wales Tidy has released a survey of graffiti across Wales and called for councils to get tough on those caught defacing communities. HOW MUCH GRAFFITI IS IN YOUR AREA?
It also said the media had a part to play and said some reports tended to "glamorise" graffiti by presenting it as art.
Tegryn Jones, chief executive of Keep Wales Tidy, said: "The costly act of graffiti is not only harming Welsh pockets, but the development of an area.
"As with anyone who blights our local landscape and community, we will look to prosecute these vandals whenever possible".
The spokesman said its Graffiti Busters project had made a difference to how graffiti was tackled in the city.