The first comparative study on predicting post-test distress (conceptualised by intrusion and avoidance, measured with the Impact of Event Scale) after presymptomatic genetic testing for Huntington's disease (HD, n=25), cancer syndromes (familial adenomatous polyposis (FAP, n=23)), and hereditary breast and ovarian cancer (HBOC, n=10) is reported. The variables with the highest predictive potential of post-test distress are presented. Participants who were depressed before the test were more distressed after testing, but we found that those who were anxious before the test were less distressed, that is, had less intrusive thoughts post-test. Other factors associated with a higher level of post-test intrusion were gender (being a woman), having children, and pre-test intrusion. Religion and being at risk for HBOC were associated with less post-test intrusion. Participants who showed avoidance behaviour before the test and those who had many people available for support showed more avoidance behaviour post-test. The test result did not additionally contribute to post-test distress. The prima facie simple notion that the test result, as such, determines the distress experienced seems to be a misrepresentation of the complex reality.