Background and Objective: The WHO points out the importance to reduce modifiable risk factors for non-communicable diseases (NCDs) and monitor the underlying trends and determinants. Since diet has been identified as one of the key modifiable behavioural risk factors, it is crucial to examine associated patient characteristics that increase adherence and create long-term behaviour change. Consequently, the following research investigates possible demographic and psychosocial predictors for dietary behaviour, particularly the Mediterranean diet, in patients with type 2 diabetes (T2D) and/or coronary heart disease (CHD). Methods: A cross-sectional analysis was conducted with 792 patients at baseline (2021) of a randomised controlled trial targeting the improvement of self-management through peer-support1. Eating behaviour was analysed using an adapted adherence screener of the Mediterranean diet. Mediterranean dietary pattern score associations with sex, age, employment, migration status, education, BMI, health literacy, patient activation (level of engagement and participation in one’s own care), self-efficacy, psychological well-being, quality of life, personality traits and loneliness were investigated using multiple regression analysis. Results: Age (ß=0.234, p<0.001), migration background (ß=0.180, p<0.001), level of patient activation (ß=0.294, p<0.001) and the personality trait openness (ß=0.234, p=0.004), were predictors for Mediterranean dietary pattern score (R2=0.194). Subgroup analyses resulted in the same predictors in the T2D group (R2=0.182), whereas the CHD group showed additional significant positive associations with gender, education and the personality trait extraversion (R2=0.363). Conclusions: Predictors for eating behaviour were identified. To maximise the success and adherence of dietary interventions, identification of predictors for eating behaviour and subsequent individualised adaptation, such as the application of an integrated approach to strengthen patient activation and self-management, could prove as a useful tool to create long-term and sustainable behaviour change and reduce the preventable burden of NCDs.