Dive summary: 

• A Pew Research Center study, Teens and Technology 2013, found that while teen cell phone ownership held steady, teens who own smartphones rose to 37 percent, up from 23 percent the year before [see full infographic at AdWeek]. 
• Of those teens that have a cell phone, one in four uses it as their primary access to the Internet; that figure rises to 50 percent among teens who own a smartphone. 
• The study also showed that older girls, age 14-17, were the most likely to access the Internet primarily on their cell phone. 

From the article: 

"Pew Research Center study, Teens and Technology 2013, found that while cellphone ownership has held steady, 37 percent of kids 12-17 owned a smartphone in 2012, up from 23 percent the year before. Moreover, one fourth of teens use the cell as their primary way of accessing the Internet, and among smartphone owners, that figure rises to 50 percent. (Only 15 percent of adults can say the same.) No wonder that, with smartphones allowing Internet access along with talking and texting, kids more than ever always seem to be on the phone."