Online advertising has become an important part of marketing investment for firms around the globe. With the increasing use of these tools, concerns have arisen around their effectiveness. For that reason, recent research has focused on measuring online advertising effectiveness with different metrics and for different markets and categories, with a focus on the profitability of advertising. However, only a few intend to understand advertisement usefulness for consumers. Particularly, in Latin America, not many studies measure the usefulness or preferences of advertising. This chapter tries to close that gap. Using a survey applied to samples in Mexico and Colombia, authors analyse different online purchase behavior and advertising perceived usefulness and preferences. The results have implications for improving the firm´s online advertising strategy and for future research, which aims to conduct comparative studies in the field of advertising usefulness.