This article reports on a study that investigates how older adolescents cognitively utilize information on the drug, heroin. With a small group of four girls in their final year of secondary education, the study sought to: (a) establish the perceived effects of exposures to information; (b) establish how the perceived effects are associated with changes to the girls' knowledge structures; and (c) establish any patterns in relation to changes in knowledge structures and perceived effects. The study employed a quasi‐experimental, repeated‐phase approach. The girls' existing knowledge structures about the drug, heroin, were elicited and mapped, as were knowledge structures after each of three exposures to different information on heroin. The knowledge structures after each exposure were shown to change by cognitive strategies of appending, inserting, and deleting. Five types of effects, as types of cognitive information utilization, were identified, these being: Get a complete picture, get a changed picture, get a clearer picture, get a verified picture, and get a position in a picture. The study also showed that there was coherence between the effects and how these effects were manifested in changes to the girls' knowledge structures. This article also discusses important implications for information practice and instructional design.