Given the significant privacy and security risks of Internet-of-Things (IoT) devices, it seems desirable to nudge consumers towards buying more secure devices and taking privacy into account in the purchase decision. In order to support this goal, this study examines the effect of security and privacy on IoT device purchase behaviour and assesses whether these effects are sensitive to framing, using a mixed methods approach. The first part of the study focuses on quantifying the effect of security and privacy compared to the effect of other device attributes such as price or functionality, by testing a causal model with choice models that have been developed from stated choice data. The second part aims to reveal the underlying mechanisms that determine the effect of privacy and security on purchase behaviour by means of a qualitative survey. The results suggest that security and privacy can strongly affect purchase behaviour, under the circumstances that privacy- and security-related information is available and communicated in an understandable manner, allowing consumers to compare devices. Moreover, the results show that a description of security that focuses on gains is more effective in nudging consumers towards buying secure devices. Future efforts could build upon this study by comparing the effect of security and privacy to more device attributes, such as ease of use or cost reduction. The results can serve as a basis for interventions that nudge consumers towards buying more secure and privacy-friendly devices.@en