BACKGROUND Parotid tumor is an uncommon neoplasm. Only a few studies describing the sonographic features of pleomorphic adenomas and Warthin's tumors have been published, and most of those reports are based on a relatively small number of cases. OBJECTIVE To define the sonographic characteristics of pleomorphic adenoma and Warthin's tumor in the parotid gland. METHODS We retrospectively evaluated the sonographic features of 77 pleomorphic adenomas in 70 patients and 93 Warthin's tumors in 61 patients. The features included tumor size, shape, border, echogenicity, and homogeneity, the presence of a cystic area, acoustic enhancement, and the grade and distribution of vascularization. RESULTS Lobulated lesions were observed in 49 pleomorphic adenomas and 36 Warthin's tumors. The lobulated shape was observed more frequently in pleomorphic adenomas than in Warthin's tumors (P = 0.005). Cystic areas within lesions were detected in 16 (16/77, 20.8%) pleomorphic adenomas and 42 (42/93, 45.2%) Warthin's tumors (P = 0.001). Of the pleomorphic adenomas, 77.9% had grade 0 or grade 1 vascularity, while 73.1% of Warthin's tumors had grade 2 or grade 3 vascularity (P = 0.000). Flow was peripheral in 53.2% of pleomorphic adenomas. The frequencies of central perfusion and mixed perfusion in Warthin's tumors were equal (47.3% vs. 47.3%, respectively). The differences in the vessel distribution between these two diseases was significant (P = 0.000). CONCLUSIONS Ultrasound imaging characteristics, including multiple occurrences, shape, intrinsic cystic change, and the grade and distribution of tumor vessels, can be used to differentiate pleomorphic adenomas from Warthin's tumors.