The purpose of this study was to determine the effects of message involvement and product expertise on the net valence of message-related cognitive responses and attitudes of receivers of advertisements varying in degree of objective and subjective content. Hypotheses were tested in a 3 (deceptive claim strategy: an ad with primarily objective claims, an ad with an equal balance of objective and subjective claims, and an ad with primarily subjective claims) x 2 (message involvement: more or less) factorial design using product expertise as a covariate in an analysis of covariance framework. Approximately one month after responding to items concerning their product expertise, product class involvement, and attitude toward magazine advertising, subjects were assigned to one of two message involvement groups and were given one of three advertising portfolios to examine for short time during a regular meeting of their organization. Measures of cognitive response, brand and nonbrand evaluation strategy, message focus, attribute importance, and brand beliefs were then obtained. When consumers are exposed to ads with varying degrees of objective content, findings suggest message involvement positively impacts net valence of cognitive responses and brand attitudes. Under these conditions, product expertise appears to be (directly) related only to attitudes. When ads with primarily subjective claims are used, message involvement positively impacts cognitive responses of only those with more expertise. However, involvement directly impacts attitudes of consumers with more and less product expertise. Further, results among those exposed to ads with primarily subjective claims, more involved experts have more positively valenced message-related cognitive responses, but not brand attitudes, than more involved nonexperts. In addition, more involved nonexperts' brand attitudes exceed those of less involved experts. These results indicate a major assumption of the reasonable consumer criterion in deceptive advertising law may not hold and suggest public policy in this area should be modified. Further, results imply expertise effects cannot be explained by greater message involvement; the constructs appear to work independently or interactively, depending on the nature of the ad. Findings suggest expertise and message involvement constitute viable segmentation bases for advertisers considering ads with varying degrees of objective and subjective content.(Abstract shortened with permission of author.)