Sinus pericranii is a rare venous anomaly, which shows abnormal communication between the intracranial and extracranial venous systems. Sonograms of sinus pericranii in 4 children were retrospectively reviewed to evaluate the following imaging findings: the overall sonographic appearance, change in size and shape, Doppler flow pattern, and associated anomalies. All 4 patients had irregularly shaped anechoic lesions with lobulating and bulging contours. They all showed intracranial and extracranial venous communication through a calvarial defect. Two patients had changes in the sizes and shapes of the lesions, and 2 patients had bidirectional turbulent flow on Doppler images. Two patients had isolated sinus pericranii, and the other 2 were associated with Crouzon syndrome. By identifying a venous scalp mass with intracranial and extracranial venous communication and changes in its size, shape, and venous flow pattern, radiologists will be able to make a definitive diagnosis of sinus pericranii by using gray scale and Doppler sonography.