Screening for cancer can cause distress. People who perceive their risk of cancer as high may be more vulnerable to distress. This study evaluated whether participants of a lung cancer Computed Tomography (CT) screening trial with a high affective risk perception of developing lung cancer had a higher level of lung cancer-specific distress during CT screening. Furthermore, we evaluated whether participants perceived their risk of developing lung cancer differently 6 months after screening compared with 1 day before screening. A total of 351 subsequent participants of the NELSON-trial (Dutch-Belgian randomized controlled trial for lung cancer screening in high-risk subjects), who were randomized to the screen arm, were asked to fill in questionnaires 1 day before and 6 months after screening. Lung cancer-specific distress (Impact of Event Scale (IES)), generic health-related quality of life (SF-12) and affective risk perception were assessed. One day before screening, the participants with a high affective risk perception (n=47/321, 14.6%) had significantly higher (i.e., worse) median IES scores than participants with a low affective risk perception (11.5 vs. 2.0, p<0.01). Although median IES scores were significantly lower 6 months after screening than 1 day before screening, participants with a high affective risk perception still showed significantly higher IES scores than participants with a low affective risk perception (6.5 vs. 1.0, p<0.01). Six months after screening, significantly less participants (10.5%) felt that their risk of developing lung cancer was high than 1 day before screening (14.5%) (p<0.01). Levels of distress were not severe, but were elevated compared to participants with a low affective risk perception, and therefore, attention for this group is recommended.