The use of social networking sites for socializing, having fun, solving academic tasks or even getting counselling for health-related problems is now inevitable. A total of 427 medical students, who are users of social media sites, were included in the research. Data about socio-demographic, anthropometric, and self-rated items regarding satisfaction with physical and mental health were collected. Three psychological tools were also used to measure self-esteem (Rosenberg Self-Esteem Scale), body-esteem (Body Esteem Scale for Adolescents and Adults) and loneliness (UCLA Loneliness Scale). Collected data were analyzed using SPSS version 23. Students use these networks for socialization (49.0%), entertainment (31.1%) and academic tasks (19.9%), spending 3.38 ± 0.80 h per day on SNSs. Less than half of them (47.5%) compared themselves to other SNS profiles. The use of Snapchat was found to be strongly positively correlated with self-esteem, and weight status was negatively correlated with the use of TikTok. More than three-quarters declared that they exercised to lose weight or to prevent weight gain. Participants were found to have a high level of body esteem. Almost half of the students proved to have a moderate to a high level of loneliness. Age and gender were found to be important: the younger the user, the higher the scores for loneliness and feeling depressed, and the greater the number of hours on SNSs. The total score for self-esteem was significantly higher in men than in women, and male students appreciated themselves as being in a better state of mental health than women. The results prove a relationship between the use of SNSs and the presence of loneliness, self-esteem and body-esteem, with gender differences. However, the use of SNSs should not be neglected in clinical settings, and are a good means of reaching patients and providing medical and psychological intervention.