Purpose: To develop a method to determine the volume of peripapillary hyperreflective ovoid masslike structures (PHOMS) and to examine the correlation between PHOMS and anatomic optic nerve head characteristics in a large cohort of patients with optic disc drusen (ODD). Design: Retrospective, observational study of patients with ODD. Participants: Patients with ODD seen in a 3-year period. Methods: We determined the prevalence of PHOMS. We then developed a method to calculate the volume of PHOMS and measured this in all patients where radial scans on OCT were available. We analyzed the correlation between PHOMS volume and patient age, size of Bruch's membrane opening (BMO), ODD visibility, and anatomic location of ODD in the optic nerve. Main Outcome Measures: Prevalence and characteristics of PHOMS in patients with ODD. Results: In 247 (77%) eyes with ODD, PHOMS were found. Among these, 80% were in the first decade of life, 87% were in the second decade, 89% were in the third decade, 85% were in the fourth decade, 74% were in the fifth decade, 73% were in the sixth decade, 58% were in the seventh decade, 40% were in the eighth decade, and 0% were in the ninth decade. The ophthalmoscopic visibility of ODD increased with age. The volume of PHOMS decreased with age, but with no correlation to the size of BMO. The median volume of PHOMS was 0.27 mm³ (interquartile range [IQR], 0.13–0.49 mm³). Predominantly, PHOMS were observed in the nasal peripapillary area (87.5% nasal, 78.5% superior, 67% inferior, and 63.5% temporal). Conclusions: In patients with ODD, PHOMS are seen frequently, with the highest prevalence in younger individuals. The volume of PHOMS decreases with age, and PHOMS are seen more frequently in patients with superficial ODD.