The paper is based on an empirical investigation of the effects of customer disposition on two levels of expectations regarding e-service quality: adequate and desired quality. Previous research indicates that customers have distinct levels of expectations with respect to the quality they desire and the quality they will find adequate in a service. The difference between these two levels is known as the "zone of tolerance'. To investigate quality expectations concerning online service offerings, a recent study on the effect of the disposition of a customer towards traditional services and the zone of tolerance was replicated in an online context. Results indicate that online customers have the smallest zone of tolerance for the two quality dimensions they find most important: security and reliability. Furthermore, positively predisposed online customers appear to be more demanding with respect to service quality. Implications for online service providers are formulated.