The J-shaped relationship between blood pressure lowering and cardiovascular morbidity and mortality has been the topic of debates in the last three decades, especially because it has been shown that this relationship is not the same in different populations of hypertensive patients. This phenomenon is very important from a clinical point of view because it determines blood pressure cut-off values in patients with different comorbidities (diabetes, coronary artery disease, kidney disease, previous stroke). There is still no consensus about the J-shaped relationship. However, the number of studies supporting the existence of the inverse relationship between blood pressure reduction, especially diastolic pressure lowering, and cardiovascular morbidity and mortality, is increasing each year. The aim of this review is to summarize current knowledge about the J curve in a different population of hypertensive patients.