Really-new products (RNPs) create new product categories for consumers. Consumers use their knowledge of similar categories to comprehend and evaluate RnPs. This paper shows that, in addition to actual supplementary knowledge (i.e., objective supplementary knowledge), subjective supplementary knowledge and supplementary knowledge calibration play an important role in RNP comprehension and net benefits evaluation leading to RNP adoption intention. In particular, findings reveal that calibration has a positive effect on objective comprehension when concrete information is presented to consumers. Moreover, subjective knowledge has a positive effect on subjective and objective comprehension where objective knowledge has a negative impact on subjective comprehension.