Complaints on Apple's online forums said the bottom left corner of the device gets very warm.
After testing the new iPad, Consumer Reports said: "Engineers recorded temperatures as high as 116 degrees Fahrenheit [47C] on the front and rear of the new iPad while playing Infinity Blade II."
Donna Tapellini, of Consumer Reports, wrote: "During our tests, I held the new iPad in my hands. When it was at its hottest, it felt very warm but not especially uncomfortable if held for a brief period."
Most of the comments on Apple's forums said that the device was "warm" after around 30 minutes of use, with most users specifying that it was not hot.
Consumer Reports said that the iPad 2 reached a high of 104F (40C) in the same tests, a difference of 12F or seven degrees Celsius. Dutch website Tweakers.net found that the new iPad was 5C hotter in use than the iPad 2.
An Apple spokesman said the iPad was "within our thermal specifications."
Earlier this week Apple announced that it had sold three million iPads since last Friday, when the device went on sale in 10 countries, including Britain and the US.
