The increase was 145% jump from the $1.2 billion for the first half of 2012, according a report by the Interactive Advertising Bureau.
In addition to outright growth, analysts attributed part of the rise to improvements in the ability to better measure the success of mobile ads.
"Mobile advertising's breakneck growth is evidence that marketers are recognizing the tremendous power of smaller screens," said Randall Rothenberg, CEO of IAB in a statement.
David Silverman, a partner at PricewaterhouseCoopers, which authored the study sponsored by IAB, said a "profound shift" is underway in how consumers view media on mobile devices "wherever they go."
IAB defines mobile advertising as display ads, text messaging ads, search ads and audio-video spots on smartphones, feature phones and tablets.
("Tablets in Media & Marketing – The brand intimacy" will be a key session at the upcoming TabletBiz conference & expo in New York on November 13, 2013)