This experimental research was aimed to test Kamin’s blocking effect in classical conditioning of preferences applied in the advertisement area. This study was divided into three parts: preliminary Study, Experiment 1, and Experiment 2. In the Study 1, both conditioned (a false publicity brand) and unconditioned stimuli (female figure with a controlled waist-to-hip ratio) were selected. Experiments 1 and 2 consisted of training in classical conditioning of preferences and blocking effect. 17-25 year-old undergraduate students of different careers participated in the present study. According to the results, a blocking effect was observed, suggesting an explanation for different phenomena in fields such as marketing or advertisement, especially when implying brands competition.