The number of online consumers has risen significantly in Brazil in the last few years, although it still corresponds to a small share of the general Internet users. One of the reasons mentioned in the existing literature for the low level of online sales is the uncertainty of the online trading, expressed through the various risks perceived by the consumers. Due to their intangible nature, services are perceived as more risky than products, which acquire an intangible character through when displayed over the screen and making it hard for the consumer to make a proper evaluation of the product. This study is intended, through a survey carried out with a typical group of online users in Brazil, to compare the perceived risks of buying a product or a service online, and to establish the most relevant risks perceived in either situation. The outcome expresses the evidence that buying services is seen as more hazardous than buying products online. From a multivariate regression analysis it became evident that the most relevant risks of buying products online have to do with financial and performance issues, while buying services online involve financial, performance and psychological risks.