This dissertation has as object identify on online shopping: why consumers get dissatisfied, what are the main reasons of the consumers complains, through the www.reclameaqui.com.br website. On the internet channel, the consumer not only buys, but reports dissatisfaction with particular product/service, brand or company. Negative comments in the network are getting largeness when compared to other channels of communication. The method of content analysis was made by using 720 consumers’ complaints, related to three different companies with most complaints on the refered website. The collect were made randomly within one year period, from January to December 2008, on the largest Brazilian website, destined for consumer’s complaints, www.reclameaqui.com.br, enabling the grouping on complaints in 12 categories. Of the claims analyzed, much of it is located in 5 categories: failures in customer service after purchase, delivery, defective product, and the return policies and product exchange. The main cause of dissatisfaction is coming from failures in customer service after purchase. From the viewpoint of online consumers, the study identified that the analyzed complaints are preceded by unsuccessful attempts of resolution along the customer service channel. The results suggests aims to understand the categories found and their interrelation can help companies to create marketing strategies to minimize the intensity and amount of claims, since they will be better prepared to solve them.