PURPOSE: The purpose of our study was to compare the diagnostic accuracy of mammography and breast ultrasonography between fibroadenoma and palpable breast cancer and to evaluate the feasibility of ultrasonography as a primary diagnostic modality to differentiate between these two tumor types. MATERIALS AND METHODS: In 36 cases of fibroadenoma and 35 of breast cancer, all palpable and pathologically-proven, the diagnostic accuracy of mammography and ultrasonography was retrospectively analysed. RESULTS: In fibroadenoma cases, the diagnostic accuracy of mammography and ultrasonography was 53% and 80%, respectively, and the difference was statistically significant (p=0.0162). In cases of breast cancer, the corresponding figures were 74% and 82%, respectively ; the difference was not statistically significant (p=0.55). Overall, the diagnostic accuracy of mammography and ultrasonography was 63% and 82%, respectively, and this difference was statistically significant (p=0.0164). The total diagnostic accuracy of both studies was 90%, and this was significantly different (p=0.044) from that of ultrasonography (82%). CONCLUSION: In patients who have clinically palpable breast masses, ultrasonography can be recommended as the primary diagnostic modality, though for other breast lesions, mammography is the recommended primary modality.