This paper examines why and under what conditions prospective travelers complete their bookings through online services compared to other methods. The study is based on a representative survey within 1,898 Swiss households, recording their travel behavior during the entire year 2007. The results show that the likelihood of booking online increases if someone is drawn to a website to gather information in the first place, and if the product sold through the website is transparent and well-understood (either per se or because the customer is familiar with the product), or if any other booking-related communication would impose a financial charge, independent of the socio-demographic background of the prospective traveler.