OBJECTIVES The objective was to determine if digital tomosynthesis of the breast (DBT) assesses the extension of ductal carcinoma in situ (DCIS) with higher precision than mammography (MG). MATERIAL AND METHODS The local ethics committee approved this retrospective study including 26 patients with DCIS, which were rated by three radiologists. Statistics were performed using intraclass correlation (ICC) for interreader agreement and the Pearson correlation for correlation of MG and DBT. Standard of reference was the histologic extension. RESULTS The ICC was excellent. Correlation between MG and histology was 0.879 (P<.01) and for DBT and histology was 0.914 (P<.01). CONCLUSION DBT provides a slightly better estimation of the size of a DCIS than MG.