Introduction: Absence of cranial bones is a rare condition that is incompatible with life. Parietal bone agenesis has rarely been reported in the literature. We performed a search for bilateral parietal bone agenesis associated with hydrocephalus and found that this was one of the few cases in the literature. Case Report: We presented a case with metopic and sagitta suture cranioschisis mimicking bilateral parietal bone agenesis (University of Izmir of Medicine, Turkey, 05.01.2016). There is a large defective area in our case similar to parietal bone agenesis, however, it has not anencephaly. Due to all of these aspects, our case is secondary cranioschisis. We have planned three stages of treatment for this case: 1) treatment of hydrocephalus, 2) tension bands to close the cranial bones and 3) cranioplasty. Conclusions: In the determination via 3D cranial tomography the presence of the parietal bones is important because, in case of agenesis the tension band does not benefit and on the contrary it creates extra stress on cerebral tissue.