Cause related products are more and more used to encourage environmental protection and other causes. Nevertheless, these a priori win-win arrangements between firms and environmental unions through the marketing of an impure public good can generate adverse and unexpected effects. Thanks to a simple model, we identify several possible counter-productive effects such as the likelihood of over-consumption or the crowding out of direct contributions. These effects can be increased or decreased according to market structures and initial donation behavior of consumers. We also add survey evidence regarding the effects of cause related products. Several policy implications are drawn