By referring to different stages of an attribution process, this study examines how source credibility effects and opposing effects of negative information in two-sided messages can be disentangled. The findings show that disclosure uniqueness (i.e., whether disclosures in a two-sided message are given voluntarily or not) leads to both inferences on source credibility and inferences on product uniqueness. The inference on product uniqueness requires more cognitive effort on the part of the consumer than the inference on source credibility. Therefore, the effects of disclosures in two-sided messages on brand attitudes depend on the cognitive load of consumers. Consumers make either an inference on the source or on both the source and the product. The results add to previous attribution research and the two-sided message literature, showing that consumers under cognitive load can fail to make inferences on negative brand attributes in two-sided messages. © 2010 Wiley Periodicals, Inc.