Recently, there's been a surge in social media usage, leading companies to employ influencers for product promotion. Alongside human influencers, virtual influencers are now increasingly used for brand and product communication on these platforms. This research investigates the impact of human virtual influencers (HVIs) on social media user's purchase intention by using an empirical survey. In order to do so a structural model was developed. The determinants believed to positively affect purchase intention include parasocial relationship, anthropomorphism, credibility and authenticity. Age, gender and product fit were examined as moderator variables. Additionally, anthropomorphism is assumed to positively influence the parasocial relationship. Data was collected using a quantitative online survey and analysed using multiple regression analysis. The proposed conceptualization and operationalization of the constructs were analysed using exploratory and confirmatory factor analysis. The most significant and substantial factors influencing customers' intention to buy a product promoted by an HVI proved to be parasocial relationship, credibility and authenticity. The influence of anthropomorphism did not prove to be significant. Moreover, anthropomorphism has a highly significant influence on parasocial relationship. The examination of moderator effects showed no moderating effects of age. In contrast, a significant gender moderation effect was observed: the influence of parasocial relationship on the intention to purchase products promoted by an HVI was significantly stronger for women than for men. Furthermore, moderator effects can be shown with regard to the variable product fit: the influence of the parasocial relationship and authenticity on purchase intention is particularly strong when product fit is given.