This paper adopts the casual attribution theory and examines how the temporal distance and the product type influence the perceived usefulness of online reviews. In this study, products are classified into material products and experience products, and we experimentally test whether the varying time intervals can moderate the effect of product type on perceived usefulness of online reviews. The results show that for experience products the shorter (vs longer) time interval can improve the perceived usefulness of online reviews; but for material products the shorter (vs longer) time interval reduces the perceived usefulness of online reviews．The lab studies also show that the reader’s attributions about the motivations of the reviewer mediate the effect of this interaction effect on the perceived usefulness of reviews. Furthermore, this effect occurs only for positive reviews, but not for negative reviews. The findings enhance our knowledge of online product reviews, and provide a new prospective to validate online reviews for online retailing.