For digest retrieval based on similarity search in deduplication processing in a data deduplication system using a processor device in a computing environment, input data is partitioned into fixed sized data chunks. Similarity elements and digest block boundaries and digest values are calculated for each of the fixed sized data chunks. Matching similarity elements are searched for in a search structure containing the similarity elements for each of the fixed sized data chunks in a repository of data. Positions of similar data are located in the repository. The positions of the similar data are used to locate and load into the memory stored digest values and corresponding stored digest block boundaries of the similar data in the repository. The digest values and the corresponding digest block boundaries of the input data are matched with the stored digest values and the corresponding stored digest block boundaries to find data matches.