The topic of this paper is the ethics of advertising on the example of telecommunications companies in the Republic of Croatia, which is specific because consumers in this relationship are mostly tied to contractual obligations for up to 24 months and there is no big choice of suppliers. In view of all the above, the aim of this paper is to show how unethical advertising can also lead to changes in consumer behavior, and empirical research is therefore substantiated theoretically by the results obtained by random sample surveys. It has been shown that today's common practice of unethical advertising is true, but also through the theoretical part we can realize how many advertisements are made and marketed in an unethical manner, whether it was untrue, overwritten by essential facts or contained various subliminal messages. Caring for each other and for their own environment, consumers today increasingly take on the notion of consumer protection and are increasingly sensitive and also notice the practice of unethical advertising. Rapid changes in consumer behavior, frequent changes in between suppliers are largely happening today for non-compliance with the standards and principles of business ethics inside the function of advertising. Therefore, it is recommended that all the companies that are advertising, especially telecommunications because of their specifics, make the most of their efforts to advertise ethically, because when a consumer knows he is being taken care of as well as his close friends and family, when a sincere or honest advertisement is put on, when the company operates transparently and respects human dignity both in the business itself and in advertising, then the consumer becomes loyal which is truly unvaluable for a company.