The popularity of PDAs has increased signifigantly in the first quarter of 2005 due to growing interest in always-on email, according to a Gartner (gartner.com) study released Wednesday.

The rising popularity of always-on email is re-inforced by the success of RIM's Blackberry, which has become the best-selling PDA in the world. Unit sales of the device have increased by 75 percent from the first quarter of 2004, the study finds.

The brand now controls 20.8 percent of the worldwide PDA market, a solid jump when compared to the 14.8 percent market share it held a year ago. Former PDA leader PalmOne is now in second place with an 18 percent market share. Hewlett-Packard, which sat in second place last year, is now in third, its market share having sunk to 17.6 percent from its former 21 percent.

The study did not cover any devices featuring voice capabilities, focusing mainly on wireless PDAs without such features. While other studies have displayed results showing a decline in PDA sales, they did not include those with wireless, non-voice capabilities.