The association between a patient's illness representation and long-term changes in treatment adherence still needs to be clarified. AIM: to evaluate the association between the representation of hypercholesterolemia and dietary modifications over 1-year, controlling for biopsychosocial factors. METHODS: 208 hypercholesterolemic Caucasian patients. Measures of dietary intake, illness representation, and biopsychosocial factors were collected at baseline, 3, 6, and 12 months. RESULTS: two multiple regressions were performed on the 1-year change in dietary habits; one with subjects with elevated fat consumption at baseline, another with individuals with low–moderate fat consumption. Higher scores on items reflecting an accurate illness representation at baseline were associated with greater dietary modification among patients of the first group. For patients with low–moderate total fat consumption, maintenance of dietary habits was associated to lower scores on the perception of stress and symptoms. CONCLUSION: to optimize adherence, intervention on illness representation should be adjusted according to initial dietary habits.