At the time of primary diagnosis, hematological diseases often present with unspecific symptoms, and abdominal sonography is performed as part of the initial diagnostic work-up. The detection of an enlarged spleen, of pathological lymph nodes or of other findings may help to suspect hematological diseases. Also, in case of suspected lymph node enlargement, sonography may be a first step. If detection of enlarged and pathological lymph nodes leads to suspicion of malignant lymphomas, examination of further lymph node stations may give an initial impression of the stage of disease and can help in planning further diagnostic strategies. Due to its wide availability, the feasibility of bedside examination, lack of radiation exposure and easy repeatability, sonographic examinations may also play an important role in the initial work-up of anemia, leucopenia, leukocytosis, and thrombopenia as well as for the detection of complications when following up on hematological diseases.