To examine the contrast formation by noncontact atomic force microscopy (NC-AFM), we simulate images of graphite (0001) and compare them with experimental results. Important features of the experimental data like the appearance of a trigonal structure with a distance of 2.46 Å between the maxima and the experimental corrugation amplitudes are Well reproduced. The detailed analysis shows that the NC-AFM images reveal the positions of the carbon atoms as minima and the hollow sites as maxima, in contrast to a simple interpretation of NC-AFM data.