The patient with prediabetes or diabetes has a high or very high risk of cardiovascular diseases.We summarize the recent guidelines jointly published by the European Society of Cardiology and the European Society for the Study of Diabetes. In this first article, we focus mainly on the preventive approaches of cardiovascular diseases in patients with prediabetes or (type 1 or type 2) diabetes. The crucial importance of a global multifactorial strategy is emphasized and the target levels of various risk factors are updated. The management of these cardiovascular complications in presence of diabetes will be considered in a second article.