In a posting to its Web site on Friday, Apple said it will cover machines for two years from the date of purchase, up from the one year of coverage that is provided as part of Apple's standard warranty.
Users have been complaining about the issue since last fall, launching online petitions and other efforts designed to get the Mac maker to address the problem.
In October, Apple said people with the problem should contact its AppleCare service, but the company had been handling problems case by case under its standard warranty. In December the company posted more information to its support Web site, an Apple representative said.
"Last year we advised customers whose 15-inch PowerBook G4 displays exhibited faint white spots to contact AppleCare," Apple said in a statement. "To ensure that our customers are well taken care of, we are extending the repair period on these systems to two years from the original date of purchase."
The program covers a limited number of 15-inch Titanium and Aluminum PowerBooks manufactured between July and November of last year. Models that are included in the repair effort have serial numbers beginning with either V7334 or V7345 or in the range from QT331 to QT339.
Under the program, Apple pays for the cost of replacing the laptop's LCD screen as well as any shipping costs. Apple will also reimburse the cost to customers who have already paid for such a repair.
The company has also posted a method to help customers identify whether their machine is affected.
Apple has used repair programs to resolve issues in the past, including a problem with the logic board on some iBook laptops.
