The aim of this study was to examine the association between possible risk factors for excessive scarring and the formation of hypertrophic scars (HTS). Hypertrophic skin scarring remains a difficult problem in medicine and can cause considerable morbidity. Nevertheless, few extensive prospective studies have been conducted which assess risk factors in relation to HTS formation. Therefore, a prospective observational study was performed. Patients who had elective cardiothoracic surgery were followed for the duration of 1 year and information was collected about a variety of possible risk factors in these patients. The associations between the risk factors and the development of HTSs were investigated. Body mass index, ethnic background, and scar related factors are positively associated with HTS formation. Antihypertensive therapeutics and factors influencing erythropoiesis are negatively associated with HTS formation.