We come to social media to connect and make friends with people, to maintain contact and friendship with acquaintances, friends and other persons from different domains of life, to share or to receive or exchange various information, etc. The use of social media is dominated by young adults; three quarters of adults under 25 have a profile on one of the social media platforms. Social media has influenced the deletion of temporal and spatial boundaries, which have greatly conditioned the communication and flow of information. This aspect of social media has made it easier for all-day communication between partners, and thus the perception of closeness among romantic partners has also increased. In addition to the positive effects that social media has on maintaining romantic relationships, there are also negative ones, such as jealousy, adulterous behaviors, lack of trust, and the development of controlling behaviors. In addition, the poor quality of romantic relationships encourages a loss of self-control in resisting the temptations and compulsive use of the Internet. Considering the contradiction of the results in terms of the relationship between social media activity and relationship satisfaction, whether positive or negative, the main aim of this research was to examine the stated relationship in a Croatian sample of respondents. Specifically, we were particularly interested in whether there was a difference in the aforementioned relationship between the group of young adults and the group of middle-aged respondents, and in general the difference in activity on social media between young and middle-aged individuals. Additionally, one of the problems of the paper was to examine a difference in social media activity between young and middle-aged individuals. The study involved 177 subjects aged 16 to 40 years, who completed an online questionnaire containing the SONTUS scale of social media activity (Olufadi, 2016) and the RAS scale for assessing the quality of a romantic relationship (Hendrick, 1988). The results showed that young adults were more active on social media, and a statistically significant negative association was found between activity on social media during times of stress and quality of romantic relationship. There was no statistically significant correlation between total activity on social media, leisure activities on social media, or activities on social media during academic obligations with the quality of a romantic relationship; nor the difference in the aforementioned relationships between young and middle-aged subjects.