Objective The aim of the present study was to investigate whether anti-vaccination attitudes and behavior, and positive attitudes to complementary and alternative medicine (CAM), are driven by trait reactance and a distrust in medical doctors. Methods The sample consisted of 770 Finnish parents who filled out an online survey. Structural equation modeling (SEM) was used to examine if trait reactance plays a role in vaccination decisions, vaccine attitudes, and in the use of CAM, and whether that relationship is mediated by trust in medical doctors. Results Parents with higher trait reactance had lower trust in doctors, more negative attitudes to vaccines, a higher likelihood of not accepting vaccines for their children and themselves, and a higher likelihood to use CAM treatments that are not included in evidence-based medicine. Our analyses also revealed associations between vaccination behavior and CAM use and vaccine attitudes and CAM use, but there was no support for the previous notion that these associations would be explained by trait reactance and trust in doctors. Conclusions Taken together, higher trait reactance seems to be relevant for attitudes and behaviors that go against conventional medicine, because trait reactance is connected to a distrust in medical doctors. Our findings also suggest that high trait reactance and low trust in doctors function differently for different people: For some individuals they might be associated with anti-vaccination attitudes and behavior, while for others they might be related to CAM use. We speculate that this is because people differ in what is important to them, leading them to react against different aspects of conventional medicine.