Atlanta - Diet Coke has topped rival Pepsi-Cola for the first time to become the second-most popular soft drink in the country behind Coca-Cola.

It marks a victory for Atlanta-based Coca-Cola Company as its sodas now hold the top two rankings, beating out its rival PepsiCo Inc.

A study by Beverage Digest released Thursday found that Coca-Cola sold nearly 927 million cases of the diet soda in 2010. PepsiCo sold roughly 892 million cases of Pepsi.

Sales of soft drinks in the U.S. have fallen for six straight years as consumers cut back on spending and switched to healthier alternatives. While both Diet Coke and Pepsi's sold less soda, Pepsi's fell more.