Background: Orthorexia nervosa (ON) is defined as pathological healthful eating. The aim of this study was to investigate whether there is any difference in orthorexic behaviours between clinical and non-clinical groups, and in different cultural contexts.. Methods: Recruitment involved both female patients with anorexia nervosa (AN) and healthy controls (HC) from Italy and Poland (N = 23 and N = 35 AN patients; and N = 39 and N = 39 HCs, in Italy and Poland, respectively). Assessment of orthorexic behaviours was performed with the ORTO-15 test. Results: Statistically significant differences were found between Italian women in the AN and HC group, whereas no difference between Polish women in the AN and HC group was found. Both Italian groups scored significantly higher than the Polish ones on the ORTO-15. Conclusions: Differences have been found between the Italian and Polish samples, both in the percentage of individuals with orthorexic behaviours as suggested by an ORTO 15 score below the cutoff, and in the mean ORTO 15 scores in the AN and HC groups, suggesting cross-cultural differences in orthorexic behaviours, whose meaning is currently difficult to understand.