Although treatment of haematological cancer has improved significantly during the latest decades, the prognosis is poor in case of relapse or refractory disease. This review describes the chimeric antigen receptor (CAR) T-cell therapy, which has emerged as a new promising treatment principle, in which the patient's own T-cells are genetically modified to recognise cancer cells. The possible side effects are usually only transient. A commercial CD19 CAR T-cell product has recently been approved as treatment for acute lympho-blastic leukaemia in children and young adults in Denmark, and a non-commercial CAR T-cell production is being established.