As the Web becomes a part of peoples’ everyday lives, there is a growing need to understand user behaviour on the Web. Recently, the flow construct has been proposed as important for understanding the nature of user online experience. Researchers assert that the benefits of flow online include increased learning, exploratory and positive behavior, positive subjective experience, and perceived sense of control over their interaction. Overall, flow could affect outcomes such as navigation patterns and repeat visits on commercial Web sites. Although widely studied over the past years, a review of the literature indicates discrepancies among various flow models and some unclear conceptualization and operationalization of the construct. This paper examined flow according to two specific conceptualizations with respect to its measurement, and tests each conceptualization in an identical nomological network. The results indicate that there is better fit of a reflective flow model compared with a formative flow model to the study data. The results of the study may aid in the understanding of the relationships between the higher order flow construct and its first order dimensions, which may help inform system designers to better assess flow and, thus, be more conducive to flow.