Orthorexia nervosa is a name for an unhealthy obsession with healthy eating. Orthorexia has recently been suggested as a new possible diagnosis. However, there is still a limited amount of research on recognition, as well as regarding diagnosis and classification. Nowadays, the Mediterranean diet has become a more and more interesting subject because of the evidence of its beneficial effect on health. Objective: The aim of the study was to examine whether there is an association between orthorexia nervosa, physical activity, and the Mediterranean diet compliance. Materials and Methods: This cross-sectional study included 139 students from the University of Split School of Medicine. The study included 5th and 6th year students, with high response rate (92.6%). Students completed an anonymous questionnaire on lifestyle habits (diet, physical activity, sleep, stress, smoking). To identify and evaluate orthorexia in students, we used the ORTO-15 questionnaire (we used a value of <35 points as a cut-off point for the presence of orthorexia). We used the Mediterranean Diet Serving Score (MDSS) to determine adherence to the Mediterranean diet. The International Physical Activity Questionnaire - Short Form (IPAQ - SF) was used to assess the level of physical activity. The chi-square test, Fisher's exact test, Mann-Whitney U test, and Spearman's rank correlation test were used in the data analysis. Results: A total of 48 students (34.5%) met the criterion for an increased risk of orthorexia nervosa. There was no difference in the prevalence of orthorexia between male and female students. The incidence of adherence to the principles of the Mediterranean diet was quite low, totaling to only 8.6% of students. Considering the risk of orthorexia nervosa, a difference in the frequency of adherence to the Mediterranean diet was found, such as the students with orthorexic symtoms were more frequently adherent to the Mediterranean diet (P=0.023). Given the adherence to the Mediterranean diet guidelines by food groups, a statistically significant difference was found for fruits, with higher frequency of the consumption of fruits in the group of students with higher risk for orthorexia nervosa (P=0.043). For the sweets, the opposite situation was found, with 27% of students at increased risk for orthorexia nervosa who consumed sweets rarely and according to the recommendations (≤2 servings per week), while only 6.6% of students with low orthorexia risk adhered to low consumption of sweets. (P=0.001). There was no difference in the frequency of playing sports (P=0.995) or in any other type of recreational physical activity (P=0.251) associated to the higher risk of orthorexia nervosa in medical students. After classifying the level of physical activity into three levels (low, moderate, and intense), again, no difference was found with respect to the risk for the presence of orthorexia nervosa (P 0.527). On the other hand, the MDSS was statistically significant and positively correlated with moderate physical activity (r=0.180; P=0.037), walking (r=0.225; P=0.009) and total physical activity (r=0.232; P=0.007 ) as well as the grade point average (r=0.215; P=0.015). Conclusion: The association between the Mediterranean diet and orthorexia nervosa has been found, but the percentage of respondents who adhered to the principles of the Mediterranean diet was very low. The association between physical activity and the Mediterranean diet has been confirmed, but not between physical activity and an increased risk of orthorexia.