User-customization is increasingly common in electronic commerce, because both the buyer and seller potentially benefit. The user interface to implement and the influence of the interface on various process and outcome measures, however, are not well understood. We developed a Flow-based model consisting of seven hypotheses regarding the user interface and its consequents. We conducted a field experiment to test an attribute-based interface vs. a questionbased interface on three variables (perceived control, shopping enjoyment and choice satisfaction) as well as two web site intentions: intention to return and intention to purchase. Six of the seven hypotheses were supported in a parsimonious model. Variance explained was 16.3% for perceived control, 45.6% for shopping enjoyment, 59.3% for choice satisfaction and 63.1% for web site intentions. The main finding is that an attribute-based interface for retail eshopping increases the shopper's sense of control and feeling of enjoyment in the process more than a question-based interface, and thereby increases satisfaction with the outcome. This combination of influences increases the intention of the shopper to return to the web site and to purchase the item. We discuss the results and suggest areas for future research in user-customization, which may apply to many different industries that engage in online commerce.