It is important to eliminate local residual cancer to avoid local recurrence after breast conserving treatment. Many efforts have been made to detect extensive intraductal components (EICs) and small invasive foci of breast cancer by diagnostic imaging including MRI and contrast-enhanced computed tomography (CE-CT). The abilities and limitations of CE-CT are reviewed in this article. The sensitivity of EIC detection by CE-CT ranges from 76% to 88%, and specificity from 79% to 89%. The sensitivity for detecting EIC and cancerous lesions were significantly higher for CE-CT than for US or MMG. The enhanced patterns of CE-CT demonstrating EIC and small invasive foci were classified into diffuse, spotty, linear and multiple types. The differences of the size of cancerous extension by CE-CT from the pathological EIC were within 2 cm in almost all cases. CE-CT is useful for visualizing EIC and small invasive foci of breast cancer.