The thesis aims to analyze the differences and overall perception of online advertisements across generations Y and Z. In relation to studies dealing with the perception of online advertising, the challenges that marketers and internet users face, and the characteristics of generations Y and Z, hypotheses are verified in the empirical part of the research. Based on the research results, recommendations are formulated that marketers should follow when creating online ads. These recommendations attempt to improve how Generation Y and Z see ads while increasing the effectiveness of online marketing.