This study examines discourses circulating around the human papilloma virus (HPV) vaccine in different online contexts by focusing on Finnish girls’ positions in vaccination decision-making and information sources that inform it. The HPV vaccine aims at preventing HPV-related cancers, especially cervical carcinoma (Maver & Poljak, 2018). Whereas most vaccines included in national vaccination programmes are provided to children before school age, the HPV vaccine is usually offered to pre-adolescent or adolescent girls. Thus, girls are not only the objects of HPV vaccination decision-making, but can also themselves be actively involved. This has raised questions on who makes—or should make—the decision to vaccinate: is it a parental decision, that of the child receiving the vaccine, or a shared decision? As information is a fundamental resource in decision-making (Lloyd et al., 2013), another important question concerns the information vaccination decisions are based on: what kind of information and knowledge sources become important in this decision-making? The present study focuses on the ways Finnish girls position themselves and are positioned by others as HPV vaccination decision-makers in public media, on one hand, and in informal online discussions on the other. Moreover, it explores the kinds of information sources that are presented as authoritative in these settings. The overall aim of the study is to increase understanding of the ways people use and value diverse sources of information and knowledge in making a decision on a vaccine.