Advertising is a very important tool in influencing the customer´s buying behaviour. However, customers tend to have various levels of understanding and decoding advertising messages. Even though children do not have purchasing power themselves, they still create a key customer segment that can influence the purchase decision of the whole family. The paper focuses on how media usage by children and their attitudes towards advertisements determines their buying behavior. We analyze the development of their advertising literacy and the most important predictors of this development. The empirical study was carried out by designing a questionnaire which was filled by Slovak children between the age of 11 and 15. We evaluated the impact of advertising and the degree of influence of the selected types of advertising media on children's consumer behavior. We also evaluated the degree of the disruptive effect of the selected types of advertising media on children and the perception of a selected medium within gender. We identified the most and the least influential type of media and we found out that there is no significant difference within gender in the case of advertising media perception by children. According to the results, we can state that children´s buying behaviour is mostly influenced by advertising on social media platforms. Therefore, the study recommends for marketers also take into account children as consumers when they employ an advertising strategy on social media.