ComScore, which surveyed more than 30,000 U.S. mobile subscribers, found Samsung to be the top handset maker (both smartphones and non-smartphones) with 26 percent market share in the September period, up a bit from the June quarter's 25.6 percent.
Apple closed in on becoming the second-biggest handset maker, lagging LG by only 0.2 percentage points. LG's hold on the market slipped 1.1 percentage points to 17.7 percent while Apple's rose 2.1 percentage points to 17.5 percent.
Google's Android operating system, meanwhile, remained the top smartphone platform with 52.5 percent share, up nearly 1 percentage point from the second quarter. Apple came in No. 2 with 34.3 percent, up 1.9 percentage points.
RIM, Nokia's Symbian, and Microsoft's Windows Phone, meanwhile, all lost share.
The report echoes findings from other researchers, which have shown Apple and Samsung widening the gap with other rivals. The two companies control the bulk of the industry's profits, and their newest flagship devices -- the iPhone 5 and Galaxy S3 -- are helping them dominate and squeeze rivals like Motorola while low-cost handset makers like ZTE are applying pressure on the low end.
Here's a closer look at ComScore's results: