The treatment of hematological diseases such as leukemia, myelodysplastic syndromes, multiple myeloma and lympohoma has changed considerably over the last decade. Targeted therapies and individualized treatment continue to gain importance. Yet these forms of treatment can only be applied if diagnostic procedures deliver the essential information needed for such personalized medicine. Thus, the best and most successful treatment must be based on modern diagnostic techniques including a specific composition of cytomorphology, histomorphology, cytogenetics, FISH, flow cytometry and molecular genetics. Several algorithms for diagnosis and follow-up scenarios are indispensable in providing the best patient care and ensuring the optimal investment of resources.