Breastfeeding in patients with chronic myeloid leukaemia (CML) during tyrosine kinase inhibitors (TKIs) therapy is not recommended but interruption of TKI treatment may cause the loss of remission. We studied the 3 cases of pregnancy and breastfeeding in women with CML and observed that stopping treatment without major molecular response may end in haematological relapse. The concentrations of nilotinib and imatinib in maternal milk were measured and nilotinib distribution in human breast milk was demonstrated for the first time. The estimated maximal doses of imatinib and nilotinib which an infant may ingest with the maternal milk were less than the therapeutical doses. However, the unknown impact of the low dose chronic exposure to these TKIs in infants imposes the limitations on their use during breastfeeding. Breastfeeding without TKI treatment may be safe with molecular monitoring, but preferably in those patients with CML who have durable deep molecular response.