Much discussion of decision-making processes in medicine has been patient-centred. It has been assumed that there is, most often, one patient. Less attention has been given to shared decision-making processes where two or more patients are involved. This article aims to contribute to this special area. What conditions need to be met if decision-making can be said to be shared? What is a shared decision-making process and what is a shared autonomous decision-making process? Why make the distinction? Examples are drawn from the area of new reproductive medicine and clinical genetics. Possible gender-differences in shared decision-making are discussed.