Currently, the internet is the main product information source for many consumer goods, mainly because of the irruption of consumer reviews based on blogging. Messages placed on them are usually perceived as a reliable and independent source of information, compared to traditional advertising. Also, blogs are websites that have a high personal nature perception. Using a 2 × 2 × 2 factorial design, this study seeks to evaluate the effectiveness of blogging commercial messages, measuring the influence of the message sidedness, communicator expertise and advertising intent and tests their influence over advertising effectiveness (measured as credibility and behavioral intention). Results show the relevance of using two-sided messages, expert sources and unbiased (non-sponsored) messages in terms of increase blog credibility and behavioral intention toward the reviewed product. Interactions of the variables are also examined.