Knowledge models are structured representations of knowledge using symbols to represent pieces of knowledge and relationships between them, while a knowledge building community involves a collection of individuals sharing a mutual interest - the construction of knowledge. This study examines a knowledge building community involved in constructing a knowledge model through the process of concept mapping in academic instruction in a Web-based learning environment. The study aimed to explore students' usage, attitudes and limitations in utilizing concept maps as an online collaborative knowledge model. Results suggest that when using concept maps as a shared knowledge model in a Web-based learning environment, one should consider three limitations: the subjective nature of the concept maps, technological aspects and the scalability of the model.