Introductin:
Orthorexia is an obsessive compliance with the principles of healthy eating. It leads to considerable nutritional limitations due to the use of restrictive principles of nutrition, and requires skills of subordination and self-discipline. These skills are manifested by persons with the tendency towards perfectionism, for whom determination and consistency in actions are important.

Objective:
The aim of the study was to find out if there occur any relationships between behaviours indicating orthorexia and adaptive and maladaptive perfectionism, and whether there are differences according to the body mass index.

Material and methods:
Materials and Method. A total number of 607 respondents were qualified for the study, 410 (67.5%) females and 197 (32.5%) males, aged 18 – 63; mean age in females 24.6±5.9, and males 24.3±4.5. The following research instruments were applied in the study: socio-demographic questionnaire, ORTO-15 Questionnaire for assessing orthorectic behaviours, and the Polish Adaptive and Maladaptive Perfectionism Questionnaire (K PAD).

Results:
A statistically significant relationship was observed between orthorectic behaviours and perfectionism. This relationship occurred to be opposite to that expected – the higher adaptive and maladaptive perfectionism, the closer the nutritional behaviours to normal. The relationships in the sub-groups according to the BMI were also statistically significant.

Conclusions:
The occurrence of orthorectic behaviours is significantly related with perfectionism, irrespective of its type. Moreover, the differences obtained in the sub-groups according to the BMI indicate the necessity for further exploration of this phenomenon.