The falcine sinus is an abnormal anatomic structure located in the falx cerebri that is closed after birth and is rarely observed. We describe two cases of persistent falcine sinus. A 60-year-old woman presented with headache. An 11-year-old girl presented with intermittent headache and a palpable scalp mass in the middle of the high parietal area. The straight sinuses were absent in both patients. In both patients, drainage of the galenic system took place through a sinus within the falx, also known as a falcine sinus. Suspicious dysplastic tentorium cerebelli was observed in one patient. It can be concluded that a mesenchymal disorder can be the primary cause for a persistent falcine sinus.