Sinus pericranii is a vascular tumor of the head having communication with the dural venous system. The tumor enlarges with increased intracranial pressure when the patient is in the lateral recumbent position. Since Stromeyer used the term "sinus pericranii" in his report in 1850, approximately 170 cases have been reported. However, relatively few cases of sinus pericranii have been reported in association with craniosynostosis or by plastic surgeons. In this study, we report seven cases of sinus pericranii associated with craniosynostosis. There were two patients with Apert syndrome, two with Crouzon syndrome, two with oxycephaly, and one with trigonocephaly. The sites of occurrence were the parietal region in six patients and the frontal region in one patient. In either type of case, the tumor was clinically a soft subcutaneous mass of the head. The clinical characteristics of the tumor were its disappearance when the patient was in a sitting position and its appearance when the patient was in a recumbent position or crying. The patients were preoperatively diagnosed with sinus pericranii from imaging test findings, such as from magnetic resonance imaging and aforementioned clinical findings. In all cases, treatment for sinus pericranii was performed during the surgery for craniosynostosis. For patients with lesions in either site, we did not perform craniotomy, and we used a minimally invasive method of tumor excision and resection of the sites of communication using electrocoagulation. Perioperatively, heavy hemorrhage was not observed, and, postoperatively, no recurrence has been observed in any patient. In this study, we examine the etiology, diagnosis, and treatment of sinus pericranii, in particular for patients with craniosynostosis.