One of the crucial function of packaging is communication with a potential client which shapes the customer product perception. Thus, knowledge on which factors and how influence buyers could be critical in gaining market share. In the face of high market competitiveness, companies are struggling to provide distinctive marketing messages. On the other hand, they may also face unfair activities from manufacturers trying to use packaging similar to those of a well-established brand. The present paper examines similarities of packaging products from companies that newly entered the market with packaging designs of a well-known drain cleaner. Taking advantage of the cognitive psychology based methodology we determine consumers’ perceived similarities and estimate probabilities of correct and incorrect selections for all pairs of nine examined products (n?=?50). The results shows that three products decidedly exceed recommended level of similarity to the We also provide practical suggestions about possible interpretations of the outcomes. The presented methodology along with obtained findings could be theoretically and practically applied in various types of marketing activities, especially related to the design of graphical marketing messages.