Professional guidelines and practice in clinical genetics generally counsel against predictive genetic testing in childhood. A genetic test should not be performed in a child who is too young to choose it for himself unless that test is diagnostic, will lead to an intervention to prevent illness, or enable screening. It is therefore generally considered unacceptable to test young children for adult-onset cancer syndromes. However, these guidelines are challenged when clinical genetics services receive requests from adoption agencies or pre-adoptive parents for predictive genetic tests in children being placed for adoption. Testing will foreclose a pre-adoptive child's future autonomous right to choose, yet those commissioning these tests argue that adoption should form a special case. In this paper, we argue that predictive genetic testing as part of a pre-adoptive 'work-up' should be discouraged when the same test would not generally be carried out in a child who is not being adopted. We present an argument based on a principle of consistency and question those claims that privilege the adoptive process, whilst acknowledging the array of uncertainties faced by pre-adoptive parents. We suggest that if pre-adoptive testing is considered, this should only take place after prospective adoptive parents have had the opportunity to meet the clinical genetics team and fully understand the implications of the testing process.