We evaluated the visibility of hypointensity regions on susceptibility-weighted (SW) magnetic resonance imaging (MRI). A commercial simple phantom filled uniformly with a gel material was demonstrated to include small regions affected by different magnetic susceptibilities compared to their surroundings. For detection of these regions in the phantom, the three-dimensional SW imaging (SWI) technique is superior to a conventional two-dimensional gradient-recalled-echo (GRE) MRI technique. The mean contrast between the hypointensity regions and their surroundings on GRE images (T2* weighted images) of 4 mm slice thickness is approximately 88% less than that on SWI of 4 mm effective slice thickness. When the effective slice thickness of SWI is increased more than 4 mm, the contrast on SW images is decreased. While the mean contrast on SWI of 7 mm effective slice thickness is approximately 75-65% compared to that of 4 mm effective slice thickness, its contrast of 7 mm is determined to be higher than that on GRE images of 4 mm slice thickness; this suggests that the SWI technique could be applied to whole brain examination by reducing the acquisition time. The quantitative results in this article are considered to be useful for evaluating the visibility of hypointensity regions on SWI, when comparing them with GRE images and varying the effective slice thickness of SWI.