The Baader-Meinhof phenomenon is part of parapsychology and as such is difficult to investigate and prove. However, although it is not often referred to by its exact name, it is very much used as part of marketing psychology. This phenomenon (also known as the "Frequency Illusion") occurs when a person pays attention to a new word, random thought, product, or something else, and then begins to notice it frequently shortly. Exploiting this phenomenon can be extremely effective in marketing activities. This phenomenon is based on two basic principles: selective attention and confirmation bias, with the mandatory condition of using multi-channel marketing. Consistent and repetitive marketing becomes memorable, and a person begins to notice a particular product or service in different places. This psychological process works even after consumers have made a purchase and no longer need the service or product. The reason for this is word of mouth (WOM), during which a person may hear from a friend that he is looking for a similar product, and the person finds himself in the role of an accidental ambassador of the product or service. Also, special importance is attached to user reviews. In the paper, the interviewees gave their opinion on the current use of this phenomenon in marketing activities, and additional possibilities, and drew a parallel with the topic of eavesdropping on mobile devices. In doing so, they try to determine whether they are eavesdropping on every user or whether it is selective attention closely related to the Baader-Meinhof phenomenon. Considering the specificity of the topic of this thesis, the reader is trying to approach this topic in a theoretical form. Considering the power that marketing possesses, which is growing year by year, marketing efforts are becoming more and more demanding, so many experts are looking for ways to stand out and improve the results of marketing campaigns. This work is based on a qualitative analysis of the answers about the general familiarity with the phenomenon and how to use it, given by marketing students, as well as people who are employed in the marketing sector.