Optical genome mapping (OGM) is a new genome-wide technology that can reveal both structural genomic variations (SVs) and copy number variations (CNVs) in a single assay. OGM was initially employed to perform genome assembly and genome research, but it is now more widely used to study chromosome aberrations in genetic disorders and in human cancer. One of the most useful OGM applications is in hematological malignancies, where chromosomal rearrangements are frequent and conventional cytogenetic analysis alone is insufficient, necessitating further confirmation using ancillary techniques such as fluorescence in situ hybridization, chromosomal microarrays, or multiple ligation-dependent probe amplification. The first studies tested OGM efficiency and sensitivity for SV and CNV detection, comparing heterogeneous groups of lymphoid and myeloid hematological sample data with those obtained using standard cytogenetic diagnostic tests. Most of the work based on this innovative technology was focused on myelodysplastic syndromes (MDSs), acute myeloid leukemia (AML), and acute lymphoblastic leukemia (ALL), whereas little attention was paid to chronic lymphocytic leukemia (CLL) or multiple myeloma (MM), and none was paid to lymphomas. The studies showed that OGM can now be considered as a highly reliable method, concordant with standard cytogenetic techniques but able to detect novel clinically significant SVs, thus allowing better patient classification, prognostic stratification, and therapeutic choices in hematological malignancies.