NEW YORK — Worldwide shipments of PCs fell sharply in the third quarter, as some consumers spent their electronics dollars on smartphones and tablets and others held off for a new version of Windows.

One research firm also estimated that Chinese PC maker Lenovo Group outsold Hewlett-Packard for the first time to become the largest seller of PCs.

Gartner said global PC shipments fell 8.3 percent to 87.5 million, while IDC said the decline was 8.6 percent to 87.8 million. Their reports came hours after a third research firm, IHS iSuppli, projected that PC shipments are bound for their first annual decline in 11 years.

PC makers began the year with hope that a new wave of lightweight laptops called ultrabooks would provide a sales lift. But ultrabooks haven’t been compelling enough to overcome the growing popularity of smartphones and tablet computers. Those mobile devices are reducing the need for consumers and businesses to buy new PCs or replace older ones.

Gartner and IDC agreed that Lenovo was the only one of the top four PC makers that saw an increase in shipments, thanks to low prices. Lenovo vaulted onto the international scene when it bought IBM’s PC division in 2005. It’s been the No. 2 PC maker in the world for a few years, behind Hewlett-Packard.

As the year winds down, the PC industry is now counting on an upcoming makeover of the Windows operating system to revive interest in desktop and laptop machines.