As a result of the rapid development of information and communication technologies, customers have gained access to a wide range of new services on the Internet. The present study focused on online travel services as one of the largest e-commerce domains. The aim was to investigate the dimensions of online travel service quality by adapting and extending the SERVQUAL model. We investigated the impact of accessibility, navigation, design, reliability, responsiveness and customization on online service quality perceptions. Where traditional service quality perceptions are based on an evaluation of encounters between service provider and customers, online service quality perceptions appear to be generally based on evaluations of the interaction between the customer and a user interface. Each online service provider employs standardized interfaces and technology for its customers. Delivering online services right the first time every time is crucial. Imperfections in technology or user interface design have immediate consequences for online service quality perceptions in all dimensions. Furthermore, customers’ zones of tolerance are likely to be smaller for online services, because a multitude of providers are available on the Web.