Myelodysplastic syndrome and acute myeloid leukaemia are neoplastic diseases caused by genetic alterations of the haematopoietic stem cells. Advances in sequencing techniques have led to a profound understanding of the underlying pathogeneses. Somatic mutations and chromosomal aberrations can be found in > 90% of the cases. The improved understanding of the pathogeneses has translated into better risk stratification and drug development. Somatic mutations may affect targetable protein-kinases or neomorphic enzymes, and new treatment options for specific molecular subgroups of patients are in the pipeline.