Before Internet consumers make buying decisions, several psychological factors come into effect and refect individual preferences on products. In this paper, the authors investigate four integrated streams: 1) recognizing the psychological factors that affect Internet consumers, 2) understanding the relationship between businesses' e-marketing mix and Internet consumers' psychological factors, 3) designing an ontology mapping businesses' e-marketing mix with Internet consumers' decision-making styles, and 4) developing a shopping agent based on the ontology. The relationship between businesses' e-marketing mix and Internet consumers' psychological factors is important because it can identify situations where both businesses and Internet consumers benefit. The authors' ontology can be used to share Internet consumers' psychological factors, the e-marketing mix of online business and their relationships with different computer applications. © 2010, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited.