In pushing the bill, city officials said that the earlier people began smoking, the more likely they were to become addicted. And they pointed out that while the youth smoking rate in the city has declined by more than half since the beginning of the mayor’s administration, to 8.5 percent in 2007 from 17.6 percent in 2001, it has recently stalled.

Besides raising the age to buy cigarettes, the Council also approved various other antismoking measures, such as increased penalties for retailers who evade tobacco taxes, a prohibition on discounts for tobacco products, and a minimum price of $10.50 a pack for cigarettes and little cigars.

The new law is a capstone to more than a decade of efforts by Mr. Bloomberg, like banning smoking in most public places, that have given the city some of the toughest antismoking policies in the world.

In one concession to the cigarette industry, the administration dropped a proposal that would force retailers to keep cigarettes out of sight. City officials said they were doing it because they had not resolved how to deal with the new phenomenon of electronic cigarettes, but others worried that if the tobacco industry lodged a First Amendment challenge to the so-called display ban, it could have derailed the entire package.

The smoking age is 18 in most of the country, but some states have made it 19. Some counties have also adopted 19, including Nassau and Suffolk on Long Island. Needham, Mass., a suburb of Boston, raised the smoking age to 21 in 2005.