Many young people place alcohol-related posts on social networking sites (SNS) which can result in undesirable effects. Although several recent studies have investigated the occurrence of alcohol-related SNS use, it is neither clear (a) what type of alcohol posts are placed on SNS, (b) the motivations to place alcohol posts, nor (c) which young people are most likely to place alcohol posts. This study addressed these three goals. A large cross-sectional study among young participants (12–30 years; N = 561) assessed the posting of different types of alcohol posts, the motivations to (not) post these posts, and potential differences in posting between subgroups (i.e., in terms of age, gender, and religion). Participants reported that they most often placed moderate, instead of more extreme, alcohol posts, in particular, when alcohol was present in the post “by chance”. Furthermore, they indicated to post alcohol-related content mostly for entertainment reasons. Finally, we found differences in self-reported posting and motivations to post according to age, gender, and religion. These findings provide relevant implications for future interventions aiming to decrease alcohol posts, for example, by making participants aware of their posting behavior and by targeting specific at risk groups. Future research should explore the effectiveness of such intervention strategies and should investigate whether alcohol posts lead to an underestimation of alcohol-related risks.