To provide healthcare professionals with clear guidance on situations when the use of irradiated blood components is indicated. The term ‘blood component’ means the therapeutic constituents of human blood (red cells, white cells, platelets and plasma) that can be prepared by various methods (JPAC　https://www.transfusionguidelines.org/red‐book/definitions). The multidisciplinary writing group developed evidence‐based clarification and practical guidance in clinical areas of ambiguity. Publications relating to patients of all age groups have been assessed. The guidance may not be appropriate in all patient situations and assessment of individual circumstances with the appropriate risk assessments and patient involvement may lead to alternative decisions.