The research was concerned with three questions: - Are there differences in ethical attitudes of students of economics universities and of universities of a general profile? - Does studying at an economics university influence students’ ethical attitudes? - In particular, does studying marketing (which stresses the need to respect ethical norms in business relations) influence students’ ethical attitudes? Research revealed some small differences between the attitudes of a Polish economics university (WSE) and a Polish university with general profile (WU). In WSE students, if compared to WU students, the acceptance of norms of code of ethics was lower, and the acceptance of violation of these norms in practice was higher. It occurred that studying at an economics university influenced students’ ethical attitudes. WSE students’ attitudes towards ethical norms improved with the advancement of studies, while their attitudes towards unethical business behaviour deteriorated. The same regularity, only slightly stronger, was observed concerning the influence of studying marketing. Students displayed significantly lower ethical attitude towards unethical behaviour than in the declarations of acceptance of respective ethical norms. This phenomenon was termed erosion of ethical attitudes. The erosion deepened with the advancement of studies and with a growing number of completed marketing courses.