The term 'primary melanocytic neoplasm' covers a wide disease spectrum, from well differentiated meningeal melanocytoma to malignant melanoma, its most aggressive malignant counterpart. Previous reports have shown that due to the paramagnetic effect of melanin, melanocytic neoplasms show high signal intensity on T1-weighted images and very low signal intensity on T2-weighted images, with relatively homogeneous contrast enhancement. The differentiation of leptomeningeal malignant melanoma from benign melanocytoma is important because of their different prognosis but on the basis of imaging findings alone is difficult. Ultrastructural immunohistochemical analysis is a possible alternative. We report the imaging findings of rare primary malignant melanoma, revealed by noncontrast-enhanced CT as a high-density mass, and demonstrating high signal intensity on T1-weighted images, and very low signal intensity on T2WI, with relatively good contrast enhancement.