Hydroxyapatite bone cement is a versatile material used to reconstruct many types of bony surgical defects, and its applications have been widely reported in the literature. Still, complications of its use do occur. We describe 2 cases of hydroxyapatite resorption and subsequent seroma formation in patients who had undergone retrosigmoid craniotomy. The presentation in both cases mimicked a CSF leak. In both cases, the fragmented cement was removed, and the patient experienced no further complications. While hydroxyapatite cement is a highly useful product for the reconstruction of some craniofacial or skull base defects, we believe that it should not be used for the reconstruction of retrosigmoid/suboccipital craniotomies because it is associated with unacceptably high complication rates. Surgeons must exercise caution in selecting candidates for hydroxyapatite reconstruction of cranial defects.