Overall, sales of smartphones and PDA/phone hybrids nearly doubled in the last year, the study found. In the first quarter of 2005, Nokia shipped 50 percent of all smartphones worldwide and Symbian was at the core of 61.4 percent of all smartphones. That's not surprising since Nokia uses the Symbian platform for its smartphones.

The study noted that while palmOne, which is the second-leading smartphone vendor worldwide, saw its market share decrease to about 9.4 percent, compared to 16.8 percent in the year-ago quarter. However, the study noted that sales of its Treo smartphone remain strong in the U.S. About 80 percent of all Treos are sold in the U.S., the study noted. The Treo accounts for about 40 percent of the company's total shipments, an increase of 17 percent compared to the year before, according to the study.

Research In Motion (RIM), in third place, saw its smartphone shipments double in the last year while its overall worldwide market share increased from 6.4 percent to 7 percent.

Riding the worldwide popularity of Nokia smartphones, the Symbian platform's penetration increased significantly. It was part of 175 percent more phones in the first quarter of 2005 than it was in the year-ago quarter. Microsoft saw more modest gains, with its platform being used in 44 percent more smartphones this year than last.

However, the number of smartphones based on the Palm OS decreased by 13 percent in the first quarter of 2005 compared to the year-ago quarter.