California has become the first US state to ban the use of sunbeds for anyone under the age of 18.
The bill was signed by Governor Jerry Brown on Sunday and will come into effect on 1 January.
State senator Ted Lieu, who sponsored the bill, said youngsters needed to be protected from the "lethally dangerous" radiation used in sunbeds.
Many states regulate the use of sunbeds, but California is the first to ban their use for most teenagers.
The US Indoor Tanning Association told the Associated Press that under 18s made up between 5% to 10% of its customers and the new law would hurt businesses.
Governor Brown's office said the bill was part of a cluster of legislation he had signed designed to "improve the health and well-being of Californians".
Under current law in California, children under the age of 14 are already banned from using sunbeds but those aged between 15 and 17 can use them with permission from their parents.
Texas has banned the use of sunbeds for youngsters under the age of 16, and other states are considering a ban for under 18s, Senator Lieu was quoted by AP as saying.
He said a higher age limit was needed because of evidence showing the cancer-causing effects from the "ultraviolent-emitting radiation" from sunbeds - particularly for those using them from a young age.
"If everyone knew the true dangers of tanning beds, they'd be shocked," he said. "Skin cancer is a rising epidemic and the leading cause of cancer death for women between 25 and 29."
In 2009, the World Health Organization's International Agency for Research on Cancer (IARC) concluded that sunbeds are "carcinogenic to humans" and moved them into its highest cancer risk category.
It made its decision following a review of research which concluded that the risk of melanoma - the most deadly form of skin cancer - was increased by 75% in people who started using sunbeds regularly before the age of 30.
England and Wales introduced a ban on the use of sunbeds for under 18s in April 2011, following a similar ban in Scotland. Brazil has banned the use of sunbeds completely.