Apple shipped nearly 23.4 million mobile computers in the fourth quarter of 2011 (Q4’11), up 128% year-over-year (Y/Y), and over 62.8 million mobile computers in 2011, up 132% Y/Y according to preliminary results from the latest “NPD DisplaySearch Quarterly Mobile PC Shipment and Forecast Report” (http://www.npdgroup.com).

Nearly 80% of Apple’s mobile shipments were iPads, more than 18.7 million shipped in the quarter, up 156% Y/Y, and 48.4 million units for the year, up 183% Y/Y. Overall mobile computer shipments grew 12% Q/Q and 44% Y/Y, reaching 88 million units in Q4’11. This was driven by continuing strong demand for tablets.

Tablet shipment growth was 42% Q/Q (quarter-over-quarter) and 210% Y/Y, reaching 31.7 million units in Q4’11. Notebook shipments were flat Q/Q but up nearly 11% Y/Y, reaching 56.3 million units. As expected, consumer mobile computer adoption was focused on tablets, holding up demand in notebooks.

“Mobile computer brands read the writing on the wall in the fourth quarter,” says Richard Shim, NPD DisplaySearch senior analyst. “Consumer demand for notebooks was expected to be weak following modest back-to-school results, especially with the expected launch of Windows 8 on the horizon, and increasing interest in tablet computers. As a result, brands focused their typical holiday price cuts on tablets to boost demand.”

Apple’s 26.6% share in Q4’11 is largely due to its dominant position in tablet computers, which propelled it to nearly three times the shipments of HP. The other brands in the top five market share rankings relied almost exclusively on notebook shipments to establish their positions.

HP maintained the top notebook computer ranking with a 15.5% share, although it lost some of its lead as shipments into North America, China, Latin America, and Asia Pacific faltered. Dell and Acer essentially tied for second place with 11.8% each. Dell had strong results in EMEA (Europe, the Middle East and Africa), while Acer continued to struggle in the notebook market.

Lenovo continues to build on momentum started early this year with strong growth in China and Asia Pacific with a dip in North America, and maintained its #4 position in notebook computers, gaining some share in Q4’11. Apple leapfrogged over ASUS and Toshiba to capture #5 with 8.3% market share.

In the tablet market, Apple continued its strong growth across all its regions, capturing 59.1% share in Q4’11. Newcomers Amazon and Barnes and Noble firmly planted their flags in the market, at #2 and #5, respectively — Amazon with 16.7% share and Barnes and Noble with 3.5%. Both brands focused on North America in their market entries. Samsung improved in all its key markets, particularly EMEA, helping it to reach .67% market share. ASUS continued its strong results in North America, EMEA, and Asia Pacific as it took 4.6% share in Q4’11.