Magnetic resonance imaging (MRI) to date remains the only imaging modality allowing direct visualization of the bone marrow compartment, in general having high sensitivity for bone marrow abnormalities. However, signal intensity changes in many different diseases presented with diffuse bone marrow infiltration show more overlap than difference, resulting in poor specificity. Therefore, MRI cannot be applied for initial diagnostic purposes in most diseases but should be reserved for staging, monitoring of therapy, and detection of disease recurrence after treatment. Diffuse infiltrative disease occurring at the hematopoietically active bone marrow, the vertebrae, pelvis, and femora should be areas included in imaging studies at a minimum if whole-body imaging cannot be applied. In this article, in-depth information is provided on selected topics, including Gaucher's disease, Hodgkin's disease and non-Hodgkin's lymphoma, chronic lymphocytic leukemia, and changes in bone marrow after different medication strategies, with overviews of the field provided by multiple recent papers in the literature.